Rocca Sonora Fortress The Rocca Sonora is a fortress, whose origins probably date back to 975 A.D., and is an example of military architecture with a triangular floor plan. Every vertex of the fortress corresponds to a circular trunk-conic tower that communicates with the other towers through underground passageways. The Rocca, which in the course of time has not undergone significant changes, preserves its original aspect: the Keep has lost its patrol walkway roof and parapet, but inside has preserved its irregularly arranged rooms unchanged, where it is possible to identify the original purpose.