Herod's harbor at Caesarea (ca. 23—15 B. C.E.) was an amazing engineering feat that resulted in the largest artificial harbor ever built in the open sea up to that point. It consisted of a large outer harbor and a smaller, more sheltered, inner harbor. The harbor was created by building two breakwaters extending out into the sea. The breakwaters protected boats from rough waters and created a barrier against the prevailing currents, which come from the south and bring silt from the Nile Delta. For this reason, the southern breakwater was much longer (ca. 2000 feet) than the northern one (ca. 800 feet). Passage through the breakwaters was from the northwest. Silting was a constant problem, kept at bay in antiquity only by the repeated dredging of the harbor. By the early Islamic period, the inner harbor had silted up and was covered with buildings. Since then, earthquakes, the rising level of the Mediterranean, and a possible tsunami have submerged both breakwaters.
Underwater excavations at Caesarea indicate that the breakwaters were constructed using the latest innovations in Roman concrete technology. Herod imported hydraulic concrete from Italy, which contained a special type of volcanic ash that allowed the concrete mixture to harden underwater. To make the breakwaters, Herod's engineers constructed enormous wooden boxes or formworks, which were towed out into the open sea. The concrete mixture was poured into the wooden formworks, causing them to sink to the sea floor, where the concrete hardened. A series of buildings was constructed on top of the breakwaters, including horrea (sing. horreum), warehouses to store the goods brought in and out of the harbor. Towers at the ends of the breakwaters marked the entrance to the harbor. One of them was a lighthouse that Herod modeled after the Pharos of Alexandria — one of the seven wonders of the ancient world — and that he named the Drusion, in honor of Augustus' stepson Drusus (father of the emperor Claudius).
8.2 Reconstruction of Herod's harbor at Caesarea. National Geographic Image ID 18651, by Robert J. Teringo/National Geographic Stock.
World History
