The Dogado was the most ancient part of the Republic of Venice, made of the lagoon from Grado in the north, to Cavarzere in the south.
The Fortress of Sant’Andrea, in the Venetian lagoon, is a unique example of Renaissance military architecture and engineering. It played an important part in the fall of Venice in 1797.
The Republic of Venice never had an actual formal constitution, much less a written constitution. Neither did it have any kind of foundational event.