The castle of Sirmione (XIII century), equipped with towers and crenelated walls, was the basis for strategic control of the lake. The famous sirmionese castle was built during the Scaligero time and its dock - still in perfect state of preservation - represents a rare case of fortification, used as a harbour. The keep was built in the thirteenth century probably by Mastino I della Scala. The imposing manor, completely surrounded by water, has an internal porch where there is a Roman and medieval lapidary; a staircase of the second compound, which is accessible through a drawbridge, goes to the walkways on the walls: here you can admire the picturesque harbour, an ancient sanctuary of Scala fleet.
The doors were fitted with different systems of closure: the drawbridge, the metal door and, in more recent times, the door to two flying focuses on hinges. Sirmione, thanks to its border location, becomes focal point of the Scaligero defence and control system and will remain so until XVI when its place will be taken by Peschiera. Venice includes Sirmione into its Republic in 1405 and immediately strives to make the fortress of Sirmione even more secure reinforcing the walls and widening the obsolete Scala dock.