Ancient History & Civilisation

13. Inca Solar Orientations in Southeastern Peru

Steven R. Gullberg, Ph.D.

Centre for Astronomy, James Cook University, Townsville, Queensland 4811, Australia, College of Liberal Studies, University of Oklahoma, Norman, Oklahoma, 73072, USA


The Incas venerated many features of both natural and man-made landscapes that they felt to possess supernatural powers. In Quechua these shrines were known as huacas, and soon after conquering the Inca Empire the Spaniards began a campaign against indigenous religion that included a systematic eradication of such shrines. Those that were large carved stones and outcroppings survived, however, and form part of this study. Many were found to have astronomical meaning, marking events such as the solstices and equinoxes.


The Incas practiced solar worship and considered their emperor to be the sun’s direct descendant, “the son of the sun.” As such, evidence of astronomical veneration should abound and this study searched for solar orientation in features found at 29 sites surrounding Cusco, within the nearby Sacred Valley, and in the area between Machu Picchu and Llactapata (Figures 1 and 2). The sites selected were taken from those presented by Bauer (1998), Hemming and Ranney (1982), Gasparini and Margolies (1980), and Malville (personal communication).

Many features of the Andean landscape were worshiped by the Incas as they felt them to be endowed with supernatural powers. Cobo (1990 [1653]: 44-45) stated that the Incas venerated large trees, roots, springs, rivers, lakes, hills and mountains. He continued “They also did reverence to these places and made offerings,” and that they worshipped anything natural that was perceptibly different. “All of these idols were worshipped for their own sake, and these simple people never thought to search or use their imaginations in order to find what such idols represented.” These shrines were called huacas and were systematically worshipped and cared for and were integral parts of Inca religion and culture. They often were shrines to ancestors who, it was believed, could influence the living. The most powerful huacas required maintenance, care-taking, and offerings. Salomon and Urioste (1991: 17) state that “a huaca was any material thing that manifested the superhuman: a mountain peak, a spring, a union of streams, a rock outcrop, an ancient ruin, a twinned cob of maize, a tree split by lightning.” Twenty-three of the sites studied were either carved rock huacas or sanctuaries that included carved or otherwise significant rocks. The remaining six sites were huacas or sanctuaries with structures, but lacked intrinsic rock shrines. These rock and non-rock huacas were categorized further as to whether or not they exhibited any potential astronomical orientation. Field research in the Region Surrounding Cusco included huacas at 19 locations, seven sites were in the region of the Sacred Valley, and the remaining three sanctuaries were related to Machu Picchu (Figure 2).


Figure 1. Peru and Cusco (modified from Zuidema, 2008).

Many facets of Inca astronomy were examined. Photographic evidence of light and shadow effects was recorded and solar orientations were cataloged. Research considered astronomical sightlines and/or light and shadow effects at times of the solstices, equinoxes, and zenith and anti-zenith (nadir) suns. Zenith passage occurs within the tropics on the two annual dates when the sun is directly overhead and vertical objects cast no shadows. The anti-zenith, or nadir, occurs on the two dates when the sun is directly beneath the observer on the opposite side of the world. This cannot be viewed directly, but Zuidema (1981b) describes Inca marking of the anti-zenith as taking place with a solar horizon observation when the sun sets 180° from the position where the sun rose on the day of zenith passage.


Figure 2. Locations of the research sites listed in Tables 1, 2, and 3. The remaining sites in the Region Surrounding Cusco that are not depicted here due to scale are located near Cusco (lower right) on its northern through eastern sides (modified from Hemming and Ranney, 1982).


The solar horizon orientations of azimuth and elevation were measured by using a sighting compass and supplemented where necessary with a surveyor’s transit. GPS coordinates of latitude, longitude and altitude above sea level were recorded at all locations for subsequent trigonometric comparisons. Orientations of features for sunrise or sunset at significant times of the year were documented. Specific locations of sunrises on mountainous horizons were accounted for with spherical trigonometry. Light and shadow effects at the huacas were recorded by digital imagery.

Huacas were first classified by region and then divided into two groups – those that were or included rock shrines and those that didn’t (Tables 1, 2, and 3). Further division regarded astronomical orientations, or lack thereof. For the purposes of this study a huaca was considered astronomical if it, or an element of it, was found to have a solar light and shadow effect or orientation(s) related in any way to the sun. If an orientation was found to exist and was available for potential use it was included. This was the case with certain east-west alignments that might have been used at the time of the equinoxes, even though it remains to be proven that the Incas were concerned with horizon positions of the sun on those days.

Table 1. Huaca Classifications for the Region Surrounding Cusco.



Solar orientations were found to be common in the huacas of this study. Of the 29 shrines examined 23 were found to fit at least one of the specified criteria. Sixteen of the sites included ceremonial rocks with solar orientations and seven more had structures oriented with the solar horizon. The sixteen sites that include rocks with solar horizon orientations are categorized as “Astronomical Rock.” The remaining sites displaying celestial alignments were placed in the “Astronomical Non-Rock” category. Five sites with boulders displayed no evidence of solar orientations and were categorized as “Non-Astronomical Rock.” These mainly were huacas among those in the study closest to Cusco and likely served purposes independent of the sun. One site without a rock or specific solar alignment was placed in the “Non- Astronomical Non-Rock” category. The existence of astronomical orientations at 79% of the sites studied supports that many Inca huacas were associated with solar observation and ceremony. If equinoxes are discounted then this figure lowers to 72%. Percentages are shown graphically in Figure 3.

Table 2. Huaca Classifications for the Sacred Valley Region.


Statistics regarding the specific types of solar events observed at the individual huacas are of particular interest. Nineteen of the solar huacas were found to exhibit orientations for the solstices and nine displayed specific effects of light and shadow. Seven had east and/or west orientations that potentially included the equinoxes and five had zenith or anti-zenith (nadir) orientations (Tables 4, 5, and 6). Ten of the sixteen astronomical rock huacas had orientations for the June solstice sunrise, six for the June solstice sunset, nine for the December solstice sunrise and four for the December solstice sunset. Five had east orientations with possible utility at an equinox sunrise and three had west orientations with similar potential for an equinox sunset. There were three instances of zenith sun orientations and one anti-zenith (nadir) orientation.

The number of examples for June and December solstice is fairly even, somewhat unexpected since the solstice in December is in the rainy season when observations of the horizon on specific days would be expected to be far less reliable. There is a marked difference between the numbers of orientations for solstice sunrises in both seasons when compared to those for the associated sunsets. The data implies a much greater ceremonial interest in the rising sun.

Table 3. Huaca Classifications for the Machu Picchu Region.


Two of the seven astronomical non-rock huacas had June solstice sunrise orientations, none for the June solstice sunset, three for the December solstice sunrise and none for the December solstice sunset. Of the 23 huacas with any astronomical association 22 held at least one orientation for one of the six primary solar horizon events of sunrise and sunset at June solstice, December solstice and the equinoxes. If the equinoxes are removed then this number of huacas becomes 19. There were a total of five possible examples of zenith sun alignments and two instances of potential alignments related to the anti-zenith (nadir) sun. June solstice sunrise orientations were noted 19 times in all (including multiple instances at the same site), June solstice sunset 7 times, December solstice sunrise 12 times, December solstice sunset 8 times, east/equinox sunrise 10 times and west/equinox sunset 9 times.

Ninety-six percent of solar huacas appear to have incorporated direct observation of horizon events when both solstices and equinoxes are included, and 83% when the equinoxes are not.

Percentages for each solar feature per huaca category are given in Figure 3. By definition all shrines in the Astronomical Rock Huaca category had at least one orientation for a solar horizon event. Solstice sunrises played a prominent role in certain annual Inca festivals, and orientations for sunrises on the June and December solstices were found to be the most common. Astronomical Rock Huacas led or tied in all but the zenith and anti-zenith categories when compared with the Astronomical Non-Rock category. This reversal, in part, is due to the nature of the Astronomical Non-Rock sites (Tables 1 and 3) where astronomically aligned features were constructed rather than carved into rock. The overall lesser occurrence of zenith-related orientations makes this difference less statistically significant, but would seem to imply that such observations may have been less common in the more highly represented rural areas of this study, although they were reported to have been of significant interest within the limits of Cusco (Zuidema, 1981b). Clear sightlines outside the city facilitated solar horizon observations, while vertical zenith observations could readily have been performed among urban structures.

Table 4. Huaca Astronomical Orientations in the Region Surrounding Cusco. Legend: JSSR–June Solstice Sunrise DSSR–December Solstice Sunrise ESR–Equinox Sunrise



This section provides illustration and discussion of orientations found at several of the sites that were explored. Examples such as the “Eyes of the Puma” at Kenko Grande demonstrate a considerable knowledge of horizon astronomy and the degree of the creativity that the Incas were capable of in the development of their shrines. On the top of the outcrop they carved two cylinders that form the puma’s eyes and then created a fissure in a nearby wall that allows light to fall upon those carved cylinders appropriately during the June solstice sunrise in a manner that completes the “puma” visual effect (Figure 4). The puma was one of three creatures most venerated in Inca cosmology - the condor being associated with the world above, the puma with this world, and the snake with the world below.

Table 5. Huaca Astronomical Orientations in the Sacred Valley Region. JSSS–June Solstice Sunset DSSS–December Solstice Sunset ESS–Equinox Sunset


Table 6. Huaca Astronomical Orientations in the Machu Picchu Region.


The chamber within Kenko Grande exhibits traditional motifs such as niches and steps. The primary altar is finely carved and may have served in one or more types of ceremonial functions. The opening in the cave’s upper northwest corner admits light that could have been reflected by gold plates in the niche below it to illuminate the entire chamber. During the time surrounding the June solstice it also facilitates an effect of light and shadow on the ceremonial steps beneath it that are adjacent to the primary altar (Figure 5).

Lacco’s caves demonstrate the interest and ability the Incas had for solar orientation. Each of the three has altars that the Incas illuminated at certain times by the sun or moon. The Northeast Cave’s altar is fully illuminated in the early morning on days approaching, during, and following the June solstice. On the horizon shown in Figure 6 the point of sunrise emerges from the right (east) and progresses daily toward the center. At the solar standstill (when the apparent travel of the sun stops near and on the day of the solstice), the alignment of the center of the cave opening with the sunrise is striking. The sun’s rays fall directly upon the cave’s altar and reflections brightly illuminate the rest of the chamber. The point of sunrise in the center of Figure 6 has reached its maximum extent to the left. After the solstice the movement of sunrise on the horizon reverses direction and proceeds back to the right.


Figure 3. Percentages of Astronomical Orientations per Huaca Category. Legend: JSSR–June Solstice Sunrise DSSR–December Solstice Sunrise ESR–Equinox Sunrise


Figure 4. The “Eyes of the Puma” at Kenko Grande.


Figure 5. Kenko Grande’s internal ceremonial steps.


Figure 6. June solstice sunrise from Lacco’s Northeast Cave.

The Southeast and Southwest Caves incorporate specifically oriented light-tubes to admit the rays of the sun or moon. The Southwest Cave is the smaller of the two and also has a smaller altar. Its light-tube’s alignment with the path in the sky traveled by the sun and moon was shown on October 26, 2006 by the crescent moon displayed in Figure 7.

The Southeast Cave appears to have been the most prominent of the three as evidenced by the degree of workmanship in its sculpture, complete with fine carvings of a puma and snake near its entrance and the highly polished altar within its inner chamber. The altar is of an appropriate size and height for ceremony and sacrifice and is brilliantly illuminated by the sun near the time of zenith passage when it is overhead at 90° above the horizon (Figure 8).

Located between Kenko Grande and Lacco is a small huaca (Solar Horizons) with two carved circles that exhibit orientations for the horizon positions of solstice and equinox/east-west solar events (Figure 9). I first measured the east-west orientations of the circles and then recorded the additional orientations for the solstices. For reasons yet to be determined, watching sunrises and sunsets on days of the soltices and equinoxes appears to have been important here. The many seats carved upon the huaca underscore this relationship as there is at least one oriented for each of the associated solar risings or settings, with the exception of the June solstice sunset where that part of the outcrop has eroded extensively.


Figure 7. Crescent moon through light-tube of Lacco’s Southwest Cave.


Figure 8. Illuminated altar in Lacco’s Southeast Cave.


Figure 9. Orientations found at the huaca of Solar Horizons.

Spanish chroniclers recorded solar pillars on the horizons of Cusco but all were eradicated, presumably in the post-conquest Catholic purge of Inca idolatries. Their locations were recorded, but there are no extant remains in Cusco. Two pillars near the modern village of Urubamba lie above Huayna Capac’s palace, Quespiwanka, give credibility to the Cusco reports, and enable direct study of this form of horizon astronomy (Figure 10). These towers on the Cerro Sayhua ridge demostrate the feasibility of this method for marking the June solstice sunrise when viewed from the vicinity of a granite boulder in the center of the palace courtyard. Their alignment supports Bauer’s and Dearborn’s 1995 hypothesis with regard to these pillars as well as Niles’ (1999) suggestions regarding the prominence of the granite boulder and an adjacent platform, no longer extant, that she argues were central features of Huayna Capac’s palace grounds. The utility of the boulder and platform as the focal point of the plaza is supported by this orientation and, to a lesser extent, by other potential alignments with natural horizon features for the December solstice sunrise and the June solstice sunset.


Figure 10. The pillars on Cerro Sayhua.

The ceques of Cusco served as a system of intangible lines to connect, organize, and facilitate the care for the many huacas that surrounded the city. Polo de Ondegardo (1965 [1571]) tells us that each Inca village had ceques connecting shrines and it appears possible that such an organizational system may have been established at Machu Picchu, smaller but similar to the one in Cusco. Within Machu Picchu the Sacred Plaza is part of an oriention for the June solstice sunrise and December solstice sunset and might possibly have formed one end of what could have been an intentional ceque that included Llactapata’s Sun Temple and the River Intihuatana (Figure 11). An additional potential ceque is found in the alignment of Llactapata’s Overlook Temple with the River Intihuatana and Mt. Machu Picchu. These alignments of huacas near Machu Picchu lend themselves in support of the concept that ceques existed away from Cusco and ultimately may serve to validate Polo de Ondegardo’s claim.


Figure 11. Machu Picchu, Llactapata, and the River Intihuatana (modified from Malville, Thomson, and Ziegler, 2006).

The 2003 rediscovery of Llactapata has given rise to many new questions regarding the overall extent, orientation, and function of the entire Machu Picchu ceremonial complex. Its many structures represent a significant enlargement of the overall estate and lend support to the possibility that a ceque system here organized huacas similarly to the one found in Cusco. The orientation of the stone-lined channel at the Sun Temple of Llactapata with the River Intihuatana and Machu Picchu’s Sacred Plaza is impressive (Figure 12), especially so when viewed from Llactapata at sunrise on the time of the June solstice. An orientation with the first rise of the Pleiades star grouping after it emerges from passage behind the sun also exists from Llactapata’s Sun Temple. Pleiades observations were a part of Inca predictions for crop success.

The River Intihuatana (Figure 13) may have played a much more significant role in the overall complex surrounding Machu Picchu than was previously thought. An intihuatana is said to have been a “hitching post of the sun,” or a place where the sun was ceremoniously tied to prevent it from disappearing as it grew progressively lower in the winter sky. This term, however, might be a more modern invention. The River Intihuatana provides a distinct link between the structures of Machu Picchu and Llactapata and serves as a part of two axes between them. In addition to lying in line with the Llactapata Sun Temple and Machu Picchu’s Sacred Plaza, the River Intihuatana also is part of an east-west/equinox alignment between Llactapata’s Overlook Temple and Mt. Machu Picchu. These orientations emphasize the potential significance of the River Intihuatana as it is positioned at the junction of these two prominent axes. The locations of Llactapata’s Sun Temple and Overlook Temple may have been specifically selected to form these alignments.


Figure 12. Alignment from Llactapata’s Sun Temple to the Machu Picchu Sacred Plaza.


Figure 13. The River Intihuatana

5. Concluding Remarks

The Incas were practitioners of solar worship and, as such, a logical assumption is that they might have designed many of their important buildings and shrines with features related to their veneration of the sun. This study set out to find evidence of solar orientations and/or effects of light and shadow at 29 sites in southeastern Peru. Overall 23 of these sites, or 79 %, were found to have at least one astronomical orientation. Features aligned for the solstice sunrises were found to be more common than the rest and slightly more of them were associated with the June solstice than were those for the solstice in December. The solstice sunsets were also notable, but of somewhat lesser relative interest. Also found were east-west orientations and as well some related to the zenith and anti-zenith suns.

The hypothesis of this study was therefore supported. As shown by the many examples identified in the research, a picture emerges of a culture interwoven with cosmology and astronomy. The Incas possessed celestial knowledge and as solar worshippers they chose to incorporate orientations and effects related to the sun, their god, in many of their temples and shrines. The huacas of this study point to a society that was both devoted to the sun and that possessed the technical ability to use their celestial knowledge in the design of any structure or carving.

Acknowledgements: The assistance of Kim Malville was indispensible, as were the suggestions of Tom Zuidema, Ken Wright, and Bernard Bell. Carlos Aranibar provided excellent support in the field and I am greatly indebted to Mike Zawaski who assisted the project with both insight and theodolite measurements. Jessica Gullberg, Steven Gullberg II, Gregory Gullberg, and Jesus Villafuerte also contributed to the fieldwork.


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