Caesarea´s Roman Port: Construction Years and Importance

King Herod built the two jetties of Caesarea´s Roman Port between 22 and 15 BCE; and in 10/9 BCE he dedicated the city and harbor to Emperor Augustus (sebastos is Greek for Augustus). The pace of construction was impressive considering size and complexity. At its height, Caesarea´s Roman Port was one of the most impressive harbors of its time. It had been constructed on a coast that had no natural harbors and served as an important commercial harbor in antiquity; rivaling Cleopatra’s harbor at Alexandria.

The Roman historian Josephus wrote:

“Although the location was generally unfavorable, [Herod] contended with the difficulties so well that the solidity of the construction could not be overcome by the sea, and its beauty seemed finished off without impediment.”

Josephus Flavius

It was the largest on the Eastern Mediterranean coast.  When it was built in the 1st century BCE; Caesarea´s Roman Port was ranked as the largest artificial harbor built in the open sea, enclosing around 100,000 m2.

Caesarea´s Roman Port Construction techniques

The breakwaters were made of lime and pozzolana; a type of volcanic ash; set into an underwater concrete. Herod imported over 24,000 m3 of pozzolana from the name-giving town of Putoli; today Puzzoli in Italy; to construct the two breakwaters: A shipment of this size would have required at least 44 shiploads of 400 tons each. Herod also had 12,000 m3 of local kurkar stone quarried to make rubble and 12,000 m3 of slaked lime mixed with the pozzolana.

Architects had to devise a way to lay the wooden forms for the placement of concrete underwater. One technique was to drive stakes into the ground to make a box and then fill it with pozzolana concrete bit by bit. However, this method required many divers to hammer the planks to the stakes underwater and large quantities of pozzolana were necessary. Another technique was a double planking method used in the northern breakwater. On land, carpenters would construct a box with beams and frames on the inside and a watertight, double-planked wall on the outside.

This double wall was built with a 23 cm (9 in) gap between the inner and outer layers. Although the box had no bottom, it was buoyant enough to float out to sea because of the watertight space between the inner and outer walls. Once it was floated into position; pozzolana was poured into the gap between the walls, and the box would sink into place on the seafloor and be staked down in the corners. The flooded inside area was then filled by divers bit by bit with pozzolana-lime mortar and kurkar rubble until it rose above sea level.

Caesarea´s Roman Port: A Unique Way to Construct the Southern Breakwater 

On the southern breakwater, barge construction was used. The southern side of Caesarea´s Roman Port was much more exposed than the northern side, requiring sturdier breakwaters. Instead of using the double planked method filled with rubble, the architects sank barges filled with pozzolana concrete and lime sand mortar layers. The barges were similar to boxes without lids and were constructed using mortise and tenon joints. In fact, the same technique was used in ancient boats; to ensure they remained watertight. The barges were ballasted with 0.5 meters of pozzolana concrete and floated out to their position. With alternating layers, pozzolana-based and lime-based concrete were hand-placed inside the barge to sink it and fill it up to the surface.

Caesarea´s Roman Port: Its Demise

However, there were underlying problems that led to its demise. Studies of the concrete cores of the moles have shown that the concrete was much weaker than similar pozzolana hydraulic concrete used in ancient Italian ports. For unknown reasons, the pozzolana mortar did not adhere as well to the kurkar rubble as it did to other rubble types used in Italian harbors. Small but numerous holes in some of the cores also indicate that the lime was of poor quality and stripped out of the mixture by strong waves before it could set. Also, large lumps of lime were found in all five of the cores studied at Caesarea´s Roman Port; which shows that the mixture was not mixed thoroughly.

However, stability would not have been seriously affected if the harbor had not been constructed over a geological fault line that runs along the coast. Seismic action gradually took its toll on the breakwaters; causing them to tilt down and settle into the seabed. Also, studies of seabed deposits at Caesarea have shown that a tsunami struck the area sometime during the 1st or 2nd century. Although it is unknown if this tsunami simply damaged or completely destroyed Caesarea´s Roman Port; it is known that by the 6th century the harbor was unusable and today the jetties lie more than 5 meters underwater.

My Private Tours At Caesarea’s Roman Port 

One of the highlights of my tours in Caesarea National Park is checking out the port area. These days the restoration of Caesarea’s Roman Port was completed. Among other things the storeroom vaults were restored; including a modern visitor center that I think is a must if you are visiting the site. In fact, they also turn it into a small museum alongside a splendid short film about the port. On the display, you could see a cash of golden coins that were found recently dated to the 11th century CE. Probably it came from a shipwreck that crashed into ruins of the port and sunk. Also during the excavations of the port, a great number of Amphoras were found. They were used to transport commodities on ships over the sea. 

Amphoras

Also during the excavations of Caesarea´s Roman Port, a great number of Amphorae were found. They were used to transport commodities on ships over the sea. On the handles of the Amphorae; the port of origin used to be stamped. In a way, it was like the brand names of these commodities like wine that Herod imported from Italy. According to the excavations; it seems Caesarea had strong ties with major ports in the ancient world. For example, the ones in Italy; Greece; and Egypt. 

Amphorae are of great use to maritime archaeologists; as they often indicate the age of a shipwreck and the geographic origin of the cargo. They are occasionally so well preserved that the original content is still present, providing information on foodstuffs and mercantile systems. Amphorae were too cheap and plentiful to return to their origin-point and so; when empty, they were broken up at their destination.