Nevería Roxy serves hands down the best ice cream in Mexico City. It’s been around for ages and their decor hasn’t changed since, so expect to feel like you’re back in the 50’s. There are tons and tons of flavors, but don't be overwhelmed, since they're all excellent. Go for a Mexican fruit flavor, like mamey or guanabana. They have a few locations around the city, but the best one is in Polanco, a nice neighborhood full of restaurants, shops, and a beautiful park that's perfect to spend an afternoon walking around.