Though it can be a bit of a rough drive to the trailhead (or... A reeeealy long walk through the other side), the payoff is huge! Varied terrain, and a view of the sisters that's so close you feel like you can reach out and touch it! If you go at the right time of the year, you'll find wildflowers at the lake. Curving around from the north is a short path to a great viewpoint.
NOTE: don't drink the water. There's dead elk decomposing in the lake that are left over from an avalanche a few years back.