Venice in a nutshell: Canals, old buildings, gondolas, bridges, and a maze of streets. The buildings of Venice are constructed on closely spaced wood piles. The piles penetrate a softer layer of sand and mud until they reach the much harder layer of compressed clay. Under water here the wood does not decay due to the absence of oxygen, and instead is petrified as a result of the constant flow of mineral-rich water around and through it, so that it becomes a stone-like structure - most of these piles are still intact after centuries of submersion! The buildings are often threatened by flood tides from the
Adriatic Sea, and various measures either are in place or have been proposed to address this, including physically lifting the city to a greater height above sea level by pumping water into the soil underneath the city - good luck with that!