Ancient brickwork

The port was actively functioning for about 100-150 years after its construction. The study of the harbor bottom and traces of shipwrecks showed that over time, the pier of the outer harbor went under water by 5-6 meters. The reasons for this are not clear - perhaps earthquakes, or tsunamis. Most likely this happened due to the fact that the concrete blocks were laid out on the sandy bottom without any fixation and then, as a result of the action of the waves, they gradually drowned into the sand. In Kronstadt, in such cases, the blocks were laid on a foundation of wooden piles driven into the sand to the continental clay.
The photo shows details of the northern breakwater. The masonry is made of local sandstone. These brick works are 2000 years old.