Climb the obvious lime-green-lichen-covered arete. The guidebook says 5.9, which is a bit of a sandbag, but not a huge one. It could be a bit much if 5.9 is your limit, though. Pretty fun and aesthetic.
This is in EFR's guidebook in the Prison Camp/Jailhouse Rock area, on a formation called Dragon Tower. This is the first formation you see when you drop down into the canyon, and is adjacent to the short waterfalls and cool mermaid pools. During wet years, the base can be a fairly deep, froggy-filled pool. Use your better judgement if you find water at the base.