Perhaps the most runnable trail in all of the Catalina Mountains.
The trail starts at the Gordon/Hirabayashi campground off of Mt. Lemmon Highway and ends at the Romero Pass Trail junction. This trail has minor elevation changes, all of which are mostly gradual rolling hills. It does, however, present a few difficult sections for runners. The climb (or descent, depending on direction) from Romero Pass is certainly the most cardiac challenging section, but the relatively smooth set of switchbacks prevents it from being a scramble.
Running water is seasonal, and the most reliable water source is Hutch's Pool which is approximately half way and about 20 yards off the main trail.
For some history on the trail's start location name, check out the USFS data here
Deer, skunks, snakes, mountain lions, and black bears.