Right near the stadium, it's in a very convenient location for Campo di Marte residents and easy to reach from the center. It's the largest swimming complex in town, home to three pools of varying sizes (including a small kiddie pool).
In addition to cooling off, you'll spot actual Florentine families who are scarce in the historic center streets during the summertime. Italian pools are great for people-watching. If you go you will almost certainly be the only traveler present. Getting there requires a bit of hoop-jumping and most tourists would rather just suffer in the heat!
Mon-Fr: 08:00-20:00
Tu: 10:00-18:00