This metaphor is often attributed to Napoleon Bonaparte, but there is very little evidence to corroborate this factoid. According to Wikipedia, the earliest reference that Margaret Plant, author of Venice Fragile City 1797–1997 (Yale UP, 2002) could quote was "from a French guide book of 1844 which said (without citing any authority) that Napoleon said that the Piazza is a salon designed for the sky to serve as a canopy." So no corroboration, and not even the same metaphor!
The Venice Incoming blog (using the word "allegedly" when attributing the remark to Napoleon) notes that "during his time he contributed to the square by building the final part to it – the 'final wing' opposite [St. Mark's] Basilica."
© Haydn Thompson 2020