Venice is a city in northern Italy that can only be accessed from the mainland by bridge. Within the city there is no traffic, as transportation is by boat called vaporettos. Piazza San Marco is the center of Venice and lowest point, so it floods first when water levels rise. Important landmarks around the Piazza include the Basilica di San Marco, Doge's Palace, and a clock tower featuring statues and a lion symbol. The Carnival of Venice is a popular annual festival attracting visitors from across Europe seeking entertainment. Pigeons in the Piazza are accustomed to people as residents regularly feed them.