Built in 1555, the impressive Fortaleza de Santa Cruz was the first fort on Guanabara Bay. The cannons are distributed over two levels, but more impressive are the 17th-century sun clock and Santa Barbara Chapel. It takes 15 minutes by taxi to reach the fort from downtown Niterói. The ride costs about R$30. On hot days, it's best to visit the fort during the morning, when it's cooler.
Estrada General Eurico Gaspar Dutra s/n, Niterói, 24370–375, Brazil