The Diamond Lake Trail forks left from the Arapaho Pass Trail and drops elevation for a half-mile before crossing the North Fork of Middle Boulder Creek. Diamond Lake is located a mile further uphill from the bridge and scenic waterfall. This stretch of trail is on a northeast-facing slope and holds snow long after the Arapaho Pass Trail has melted dry. Turn west on a marked side trail to Diamond Lake. Continuing straight and passing the turnoff to Diamond Lake, the main trail continues for 2.4 miles, and climbs up to cross the ridge just above tree line. The return to tree line may be difficult to find - watch for rock cairns at the edge of the trees. The Diamond Lake Trail ends at Devils Thumb Trail.