|Slot canyons of the San Rafael Swell.
The northwest corner of the Colorado Plateau is a seldom explored wilderness area containing many narrow canyons amidst great expanses of colorful slickrock with arches and natural bridges, cliffs, ridges and mesas. This is the San Rafael Swell, a huge oval-shaped uplifted area bordered approximately by UT 24, US 6/191, UT 10 and the northern edge of Capitol Reef National Park, and bisected by I-70. Around the edges of the Swell is a ring of upturned eroded strata - the San Rafael Reef, where most of the slot canyons are located. The reef is steepest and widest on the east side, so here the canyons are deeper. The main area is from just northwest of the town of Green River, south alongside UT 24, past Goblin Valley State Park and further west to a particularly remote region known as the Moroni Slopes. There are over 30 canyons to explore along this part of the reef, and apart from a few near Goblin Valley (Bell/Little Wild Horse, Ding/Dang, Crack/Chute), all are remote, hidden and rarely visited. Some such as Quandary, Cable and Segers Hole require rappelling equipment and technical ability to overcome sheer drops and deep potholes.
The central area is generally flat and barren - wide open plains with occasional buttes and ridges, but is crossed by two rivers forming deep canyons with branched tributaries. Both offer challenging narrows hiking; to the north, the San Rafael River flows into the Swell from Castle Dome and soon enters a deep layered canyon, seen most easily from the Wedge Overlook, a viewpoint that offers panoramic vistas of rocks and ravines - a kind of mini Canyonlands. Several miles downstream. the river enters a much narrower gorge with two extended sections, known as the Upper and Lower Black Boxes, that provide a hiking experience comparable to the Zion Narrows or the Paria River, and with similar fast flood dangers. South of I-70 is the lesser known Muddy Creek, which also has a deep dark section of over 10 miles ('The Chute'). As with the Black Boxes, hiking involves wading in the river most of the time and at least one overnight stay is required to see all of the canyon. The creek cuts through the San Rafael Reef near Hanksville and becomes the Dirty Devil River
which joins Lake Powell at Hite.