In the 13th century Sirmione became one of the points of the Scaliger fortification system with the construction of the Castle, probably ordered by Mastino I della Scala.

During the same period, it was a refuge for Patarini heretics condemned to be burnt at the stake in Verona (1278).

The function of control and defense, assumed in the late Roman age, would continue until the 16th century, when it was replaced in its role of fortified center of the lower lake by Peschiera.
The castle would still remain a military garrison headquarters until the middle of the nineteenth century.

Sirmione is located in a strategically important position, between the plain and the southern part of the lake, bordering territory of the Scaglier realm and then, from the early 15th century, the Republic of Venice.

And it would remain linked to Venice until its fall in 1797.