San Marco is breathtakingly beautiful: hundreds of pigeons everywhere, which is also of concern due to all of the centuries-old architecture and art work (background for pigieons? could be worse both for them and for the humans...). Many people feed the pigeons, which attracts them and a number of people encourage the birds to land on them. Suggestion: ignore the pigeons and avoid getting bombed and just enjoy the beauty, history, and observing the people around.