Piazza San Marco (Italian pronunciation: [ˈpjatt͡sa san ˈmarko], often known in English as the St Mark's Square), is the principal public square of Venice, Italy, where it is generally known just as "the Piazza" (la Piazza). All other urban spaces in the city (except the Piazzetta and the Piazzale Roma) are called "campi" (fields). The Piazzetta (the 'little Piazza') is an extension of the Piazza towards the lagoon in its south east corner (see plan).
The two spaces together form the social, religious and political centre of Venice and are commonly considered together. This article relates to both of them. A remark usually attributed to Napoleon calls the Piazza San Marco "the drawing room of Europe" (the attribution to Napoleon is unproven).
The Piazza San Marco is not far above sea level and during the Acqua Alta, the "high water" from storm surges from the Adriatic or heavy rain, it is quick to flood. Water pouring into the drains in the Piazza runs directly into the Grand Canal. This normally works well but, when the sea is high, it has the reverse effect, with water from the lagoon surging up into the Square.