Mount Lemmon, Arizona

HC: Mile 17

Cat. 3: Mile 42

Cat. 4: Mile 40 and 52

Mount Lemmon is one of the top bike climbs in America in terms of elevation gain, and it can be accessed easily from Tucson.

After entering Coronado National Forest, Catalina Highway ascends 20 miles to Palisades, 25 miles to Summerhaven, and 27 miles to Ski Valley. From Ski Valley, Ski Run Road climbs another 2 miles to the observatory, which is located at 9,100 feet above sea level.

Catalina Highway is smooth with a wide shoulder and wide turns, mile markers, and a steady 5 to 6 percent grade. Only the 2 miles to Ski Valley are steeper, around 8 percent, and the last 2 miles to the observatory are the steepest, exceeding 10 percent.

Vegetation ranges from saguaro cacti at the bottom to pines and aspens at the top.