Lincoln Park Zoo is a real time commitment — fit it in only if it's a priority.
Allow 1.5–3 hours.
A genuine gem: a free, walkable zoo in a beautiful park setting, easy to drop into for an hour without the all-day commitment of a paid attraction. The honest catch is that being free and compact, it's smaller than ticketed zoos and gets packed on warm weekends — but for the price, complaints are hard to justify.