Founded in 1868, the Lincoln Park Zoo is the oldest in the United States. Perhaps best of all, it's free! The zoo has everything you'd expect out of a major urban zoo, with a wide variety of animals. There are also paddle boats that one can rent for a trip around the little lagoon. The zoo is particularly popular with children, with two parts, the Pritzker Family Children's Zoo and the Farm-in-the-Zoo, devoted especially to kids. (Of course, that also means the zoo can get very noisy and crowded, particularly on weekends when the weather is nice!)