El Charco del Ingenio Jardín Botánico
This ecological preserve and botanical garden—the largest of its kind in Mexico—is home to hundreds of rare and endangered species, cacti, and succulents. There are walking paths, temescals (steam baths), picnic areas, a cafe, a shop, a nursery, and a greenhouse. Full moon, equinox, and other cultural or environmental ceremonies take place periodically. It's a long hike up from downtown, so get a cab up and walk down. Bonus points: The Dalai Lama proclaimed it a Zone of Peace when he visited here in 2004.