This segment of the Arizona Trail is newly constructed and built to high standard. Weave through saguaros and dodge sharp rocks for over 25 miles (one way). This is an out and back ride, so turn around when you want and head back.
There are many access points, but the closest to Tucson is at Pistol Hill Road (described in directions). The trail heads southeast, around a saguaro studded hillside before dropping into Colossal Cave Mountain Park. After climbing a steep saddle, look for 'the castle' in the distance. It's a private residence, but a bizarre one. Continue on the mellow singletrack to 3 Bridges, then through a rideable culvert under Interstate 10.
The segment ends at the Lakes Road, near some dirt tanks, but construction (on the Las Colinas segment) to tie into the Arizona Trail further south is ongoing.