San Giusto Castle is located next to the cathedral. The fortress sits atop a hill, the highest point along the coast, which for thousands of years made it a strategic location for controlling the region. The castle itself was built between 1470 and 1630 by the Austrians, initially to house the city governor, and over time watchtowers were added, turning it into a defensive stronghold as well.

Renovations began only in the 1930s, after the site became city property. In 1936, a museum opened in the castle, making it a recommended visit for both its breathtaking views of the city and its historical significance.