Archaeological investigations at Arsuf are much more recent and a great deal remains to be published. The site differed from that at Caesarea Maritima, as Arsuf takes advantage of a sandstone bluff overlooking a shallow natural haven near the modern Israeli town of Herzliya.
The city had reached its greatest extent during the pre-Islamic Byzantine period when it had an important Samaritan community, though not, it appears, a Jewish one. During the early Islamic period the extent, though not necessarily the population, of Arsuf was reduced, apparently in response to the threat of Byzantine naval attack. Arsuf was now, for the first time, given a fortified wall. This was the city that the Crusaders seized early in the 12th century, after which the conquerors continued to use the existing Islamic fortifications, restoring them and adding a new gate. During the early 13 th century, the Crusaders added a castle on the edge of a cliff overlooking the sea. This included a courtyard surrounded by a high inner wall with two rectangular and four semicircular towers. An outer wall had five larger and lower bastions, the largest of which projected directly ahead of the twin gate-towers. This doubled-wall system was in turn surrounded by a deep moat strengthened by outer retaining walls forming a polygon. The seaward ends of this retaining system have, like much of the western side of the castle, collapsed as a result of cliff erosion.
A bridge on two piers led into the south-eastern side of the castle. It would originally have had a drawbridge into a short wall between the southern and easternmost outer towers. Some large circular structures in the north-eastern corner of the castle may have been ovens in a kitchen area, and on the western side was a polygonal keep over a vaulted hall. Much of the western side of the castle and all of its straight western wall have fallen down the cliff.
Although the Crusader military architects who designed the new fortifications of the town of Arsuf followed the lines of the existing Islamic defences, they added several much stronger walls and towers. Here the lower part of the south-eastern corner tower has been excavated, along with part of the moat and a retaining wall on the far right.
Above left Much of the ruins of the medieval Crusader city of Arsuf remains unexcavated, because the ground has been polluted by chemicals from an Israeli armaments factory. However, the foundations of the ruined east gate have been uncovered. Here the Crusaders followed the line of the previous Fatimid city fortifications, but added a stronger gate.
Above right The northern part of the fosse, or moat, around the citadel at Arsuf. Massive strengthening piers were added to this, the longest stretch of outer retaining wall, probably because the pressure of loose sandy earth behind threatened to burst the wall and fill the moat.
At the base of this cliff was what some have identified as a harbour with jetties and corner towers. An alternative interpretation suggests that it included a flat area of land, just above sea level, which may have served as a wharf. A tunnel led from the fortress to the supposed 'port', perhaps as a final means of escape, while another tunnel led south from the courtyard into the moat. This could have served as a postern, enabling the garrison to attack an enemy in the moat.
Above The rectangular area of very shallow water in the centre of this photograph is sheltered by the foundations of walls dating from the 13th-century Crusader occupation of Arsuf. It has sometime been interpreted as the remains of a small harbour, though it might also have been a wharf that was later flooded by a slight change in sea level. The massive pieces of masonry on the right are from the collapsed western side of the citadel overlooking this harbour or wharf.