An unusual slot canyon in tilted limestone beds at a narrows on Pahranagat Wash, a normally dry tributary to the Colorado River system. It’s blocked at the upstream end by Arrow Canyon Dam, a flood-control structure built in the 1930s by the Civilian Conservation Corps. Bypassing the dam requires either a technical climb or a lengthy detour, so it’s most straightforward to do an out-and-back from the downstream end. Sources vary, but it’s roughly three miles from the official trailhead (marked by signs and cable barriers across the canyon) to…