The city of Caesarea Maritima (meaning, the “city of Caesar by the sea”) was built by King Herod the Great on the Mediterranean coast about 70 miles northwest of Jerusalem. Caesarea was one of Herod’s massive building projects, constructed over an earlier site known as Straton’s Tower, founded in the 4th century BC by King Straton of Sidon.
According to the historian Josephus, Herod’s construction of this new and expansive city occurred between 22 and 10 BC. Caesarea’s layout was typical of other ancient Roman cities, with well-planned streets, an underground sewage system, an aqueduct, a Roman temple dedicated to Caesar Augustus, an amphitheater, and a harbor.
The harbor at Caesarea is probably its most impressive feature — believed to be the first artificial harbor in the world. It was built with a technique that used hydraulic concrete made from special volcanic sand. This sand – known as pozzuolana — was the secret ingredient that allowed the concrete to form and harden underwater. Since there was no natural harbor at Caesarea, engineers carved into the coastline and built a huge breakwater using this revolutionary technology.
The scope of construction here was massive, with concrete blocks as large as 39 feet by 49 feet by 5 feet, and some weighing more than 50 tons. The southern breakwater for the harbor extended more than 1,500 feet out into the Mediterranean Sea. Extra blocks beyond the breakwater were used as foundations for lighthouses and statues.
According to geologic analysis, scholars have determined that the concrete used at Caesarea harbor was made with pozzuolana imported from the Gulf of Naples over 1,200 miles away. It took hundreds of ships to get all that sand across the Mediterranean Sea.
In about 130 AD, an earthquake severely damaged Caesarea harbor. Within a few centuries, the harbor ceased being used at all. By the way, curing cement underwater was such a revolutionary process, that after the fall of the Roman Empire in the 5th century, the technology was lost to the entire world for hundreds of years.