Shore at the North Pier

The underwater part of the piers, breakwaters and dams of the port was composed of huge blocks of 'hydraulic' cement, consisting of a mixture of volcanic ash (pozzolana), crushed stone from local sandstone and sand. The mixture, prepared in advance on the shore, was loaded into wooden boxes, towed to a chosen place and drowned at a depth of 5-15 m. In the water the mixture hardened and turned into ancient Roman concrete, after which the next block was placed on it. Everything was like Russian Kronstadt, only 1700 years earlier.