The largest and the best-preserved Portuguese bastion in Goa was built in 1609-12, to control the entry into the river Mandovi and to protect Old Goa against invasions from the Dutch and the Marathas. Ringed by thick battlements, the heart of the fort was protected by two hundred cannons and a deep dry moat, which one still has to cross to get inside. An interesting feature of the fort is a four-storey Portuguese lighthouse, erected in 1864 and later renovated and modernised in 1976. Though the entire fort is no longer intact, some buildings that are still in good shape have been converted into a prison. En-oute to the fort, is the church of St. Lawrence, the Saint of the sailors.