Lago do Juçara is a small lake in the middle of the island, surrounded by preserved Atlantic Forest remnants. It's used as a water reservoir for the city and the surrounding area is protected. The forest trails here are good for birdwatching — herons, kingfishers, and various forest birds are common — and the shade is welcome on hot days.
The lake is accessible by bus from the centre and is less visited than the state parks, making it a peaceful alternative to the more popular outdoor spots. On weekday mornings, you might have the waterside path essentially to yourself.