Approximate location — plotted from published sources, not a site visit, and not a guarantee of access.
The Upper Black Box is a narrow gorge of the San Rafael River in the San Rafael Swell where walls rise hundreds of feet and pinch to a few dozen feet wide. From the BLM trailhead at the end of Mexican Mountain Road, the route means miles of wading and swimming through cold river water with no maintained path. A technical canyon day for prepared parties, not a casual walk.
Cultural sites and artifacts are protected by federal law (ARPA/NHPA) — stay on established routes, touch and remove nothing, and follow the managing agency's and the affiliated tribe's guidance on access.