Marvel at the size of Cathedral of St. Peter. Schedule in a service if you can or simply wander around and enjoy the peace and quiet.
You'll find this principal church in Centro. If you're looking for things to do on a budget, you'll be pleased to hear there's no entry fee. Once you've seen Cathedral of St. Peter, check out other attractions in the area. Marinheiros Island, Rio Grande Library and Dock Market are traveler favorites.