Saint Mark's Square
Piazza San Marco
In 1000 the St. Mark's Square was still a kitchen garden. Only in the 12th Century it adopted its present dimensions. The Venetians surrounded the place with houses and palaces and it was paved. The Piazzetta with its marble shores was build. Its 2 huge oriental granite columns were placed there later.

+Venice and the pigeons
The Piazza San Marco without pigeons - unthinkable! Thousands of them enjoy daily the heart of the visitors and the licensed pigeon food sellers as well - but not the locals:
Gone are the days when the doves were were on the menu, as the Venetian patriarch Angelo Roncalli, later Pope John XXIII did, who stuffed them in a pot for a pigeon soup with crusty bread, a typical Venetian specialty.
Salmonella and mites are the main cause. Outside the Piazza San Marco there is strict feed ban (which fortunately is widely respected).
But since when and why are the pigeons in Venice?
According to tradition, the old Doge Enrcio Dandolo, after the spectacular fall of Constantinople, sent a dove from the Fourth Crusade, in 1204, carrying the good news of victory for Venice. The dove has flown the 1,300 km, since then they became a part of Venice.
That there are so many of them is explained by the fact that the Venetians, in their pigeons love, went so far every year to let whole flocks of pigeons free on Palm Sunday - a custom that the lagoon dwellers, unlike other popular festivities, have been dismissed in the latest decades.