Forte São Mateus (Praia do Forte, Cabo Frio)

Forte São Mateus was requested in 1617 to replace the vulnerable Forte de Santo Inácio and to protect the settlement and the mouth of the Lagoa de Araruama channel, today the Canal do Itajuru. Built in 1620, the year it was already in operation, it gives its name to Cabo Frio's main beach, Praia do Forte. The fortification was built to protect the local population and the coast from the French, Dutch and English, who were drawn to the region in the 17th century by the large amount of pau-brasil.

From 1899 the fort served as a lazaretto, housing terminally ill patients from the epidemics that struck Cabo Frio, and by the late 1930s it was in ruins. Today it is a National Historic Heritage site: the fort, the rock on which it stands and the tip of the beach within a 500 m radius of the fort's centre have been listed by IPHAN since 1956.

In the 1980s, divers were already circling the fort on scuba, in a dive of 30 to 40 minutes. On days when the sea was very calm, snorkellers at the fort used to cross the channel to the Carolina wreck, which lies nearby. The Cabo Frio region has varied marine life.