The mythical foundation of Venice (during the feast of the Annunciation of the Virgin) is said to have occurred on 25 March 421. 421 is also the legendary date for the foundatin of the church of San Giacomo di Rialto (next to the Rialto bridge in Venice). Image: San Giacomo di Rialto. This file is licensed under the Creative Commons Attribution Share Alike 4.0 International license.