Surrounded by Atlantic rainforest, O Veleiro is a delightfully set guesthouse located on a cobblestone road uphill from Botafogo. The rooms are small and adequately furnished but the backyard is the real attraction, with hammocks, a small pool and pretty views (plus the occasional marmoset visitor).
On the downside, it's a bit of a trudge to get down to Botafogo (even more so on the way back uphill), but for a tranquil escape that's still inside central Rio, this is a decent option.