Revelin Fort was built outside the city walls, and is partially included into the defence complex of the Ploče Gate. The lower part of the fort was built in 1463, in the shape the City model held by St. Blaise on the triptych painted by Nikola Božidarević around 1500. The fort protected both the eastern part of the City from mainland and the entrance to the City Harbour. In 1538 the fort was strengthened and enlarged in the form of an irregular square according to the instructions of Italian engineer Antonio Ferramolino of Bergamo. Revelin has three entrances, and was encompassed by the moat and sea on three sides. The well-known Renaissance craftsman Ivan Rabljanin kept the foundries for casting cannons and bells in the large Fort interior. Today, the spacious fort terraces serve as venues for various performances of the Dubrovnik Summer Festival.