Why Venice Was Built on Water

[A] No one chooses a lagoon as a building site without a reason. The islands on which Venice stands are little more than banks of mud and sand, and in the sixth century they held nothing but fishermen and salt workers. [B] What drove families from the prosperous Roman towns of the mainland out into that shallow water was a series of invasions. A lagoon is useless to cavalry, and the channels through it are so shifting and shallow that a pilot who does not know them will run aground. [C] The very emptiness that made the islands poor made them safe.

Safety, however, had to be paid for in engineering. [D] A building cannot rest on mud, so the Venetians drove forests of alder piles down through the soft layers until they met firmer clay, then laid stone platforms across the tops. Submerged in oxygen-poor mud, the timber did not rot; in places it slowly took on the hardness of stone. The result was a city that could carry marble churches on a foundation of trees, and that grew rich precisely because the sea it sat in was also its road to the East.