The Lenawee Trail leaves Arapahoe Basin near the top of Zuma Lift. Mountain bikers often ride up the front side of A-Basin and head down the Lenawee Trail, dropping 2000+ vertical feet to Peru Creek Road near the town of Montezuma. It is very difficult ride, but some people absolutely love it. Hikers often walk the trail in the opposite direction, climbing into the alpine.
A buddy of mine took this photo yesterday. Walking or riding, this one should be on your list.