Some folks here have a sense of humor.
The frescoes on the walls of the former city hall are done in the "trompe l'oeil" style, except for one cherub's chubby 3-dimensional leg hanging out over the ledge.
And the door isn't an optical illusion. The road does indeed slope slightly up to the right, while the building itself (standing next to a canal) leans emphatically down to the right. Apparently the owner decided it would be far cheaper to modify the door slightly than to shore up or rebuild the building.