The city of Venice is built on millions of wooden stakes.
Why it is true
Venice sits on millions of oak and larch wooden stakes buried in mud. The lack of oxygen in the mud prevents the wood from decomposing, keeping it intact for over a thousand years.
Source: Architecture
Would you rather be asked first?
This is the reading side of the site, so the answer is in the sentence above — that is the whole point of it. Test yourself works the other way round: the question comes on its own, and the fact and the explanation only appear once you have answered.