Sabino Canyon is the closest thing Tucson has to its own national park. A narrow desert canyon cut into the Santa Catalina Mountains on the city's northeast edge, it has a paved road (no private cars allowed) that climbs through saguaro forest, palo verde groves and mesquite to a wide turning loop with cliffs above and a small creek below.
A shuttle tram takes you up in about half an hour with running commentary and drops you at trailheads along the way; you can ride the whole loop or hop off and walk back. Mid-March to April the wildflowers bloom; the prickly pears flower a little later. The longer trails connect up to Mount Lemmon for serious hikers. Bring water — there is little shade, and rattlesnakes and Gila monsters live here.