To make the islands of the Venetian lagoon fit for habitation, Venice’s early settlers needed to drain areas of the lagoon, dig canals and shore up the banks to prepare them for building on. They began by digging canals and lining them by driving closely spaced wooden stakes – many of them made from water-resistant alder wood – through the sand and mud to rest on the harder clay beneath. On top of these stakes, they placed wooden platforms and then stone, and this is what the buildings of Venice are built on. Source: www.venezialines.com