Desolation Lake is a large mounain lake without an outlet.  It is fresh water, because the water drains out through glacial deposits which formed the lake's basin.  The trailhead is 9.6 miles up Big Cottonwood Canyon on the north side of the road, just across the road from the turn off to Donut Falls.

The trail starts by heading parrallel to the road for 1/4 of mile before it enters the Mill D North Fork drainage and heads north.  It stays on the west side of the drainage for 3/4 of mile where the trail splits.  The left fork heads to Dog Lake.  The right fork heads to Desolation Lake.

From the junction the trail makes a switchback, then joins the east drainage near an overlook.  There are great views of the south side of Big Cottonwood Canyon.  The trail goes through a meadow and past a small pond, then north east through the woods before it climbs a final hill to reach the lake in an open cirque.