Venice's centuries-old buildings rest on millions of wooden piles

Venice was built across more than a hundred lagoon islands by driving tightly packed wooden poles into soft marshland to create firm foundations. The Rialto Bridge alone rests on about 14,000 piles, while roughly 10,000 oak trees support St Mark's Basilica. Waterlogged, oxygen-poor soil has slowed rot for centuries, though flooding and rising seas now threaten the city.