About as deep into the Wind Rivers as you can go, Peak Lake is the forgotten cirque just north of Titcomb Basin and southwest of Gannett Peak. It's hard to get to from any trailhead; I'd advise the Doubletop Mountain trail,
which is least rugged. The approach from Elkhart is not too bad, either.
Cube Rock Pass on the Vista Pass trail entails 5-foot unstable talus. Sheila Pass is high but quite walkable. The trail around the
north side of Peak Lake is no more: recent rockslide has obliterated it, and don't even *think* about trying your luck on the new talus cone unless you are a strong swimmer.
The south edge of the lake is ugly but negotiable.
Rock here is mostly metamorphosed granite with heavy intrusions of gniessic stone; you may encounter wide bands of decomposed rock between sections of bullet pink granite.