Catalina State Park covers 5,500 acres at the foot of the Santa Catalina Mountains on Tucson's far northern edge. The cactus forest is dense — nearly 5,000 saguaros — and the trails range from easy nature loops to the strenuous climb to Romero Pools, a series of natural rock pools deep in the canyon that hold water after winter rains.
The Romero Pools trail (3.5 miles, around 1,000 feet of climbing) is the classic walk here; go early in spring when the pools are full and the wildflowers are at their peak. Hummingbirds, javelinas, and the occasional desert tortoise are common. There is a small day-use fee, plus a campground that fills up months ahead in the cool season.