Aqua Caliente lies between the Rincon mountains and the Santa Catalina mountains. It’s a lovely 9 mile round-trip hike, except for maybe the last section up the final slope to the summit. Many people hike just the first 3 miles to the saddle and then return.
Drive east along Tanque Verde, past the turnoff to the Catalina Highway and Mount Lemmon. Continue for 1.9 miles past Houghton Road, then turn left on Soldier Trail. Continue north for 1 mile to Fort Lowell Road. Turn right on Fort Lowell and drive east for 1.3 miles (Fort Lowell eventually becomes Camino Ancho), then turn left on Camino Remuda. Follow Camino Remuda for 0.5 miles to the Agua Caliente trailhead on the right.
Follow the obvious trail for 3 miles as it zig-zags up the hill, then rolls up and down and finally climbs steeply to the saddle and a metal signpost.
Turn right and follow the ridge for 1.5 miles to the top. After an initial climb the ridge flattens and you walk through a beautiful grassy meadow. The ridge steepens again and eventually runs out, and you climb the final tree-covered flank of the mountain. The trail here is the roughest and least pleasant part of the hike, but the top of the mountain is lovely, with great views.