Half an hour southeast of Tuba City along Arizona Route 264, an unsigned pullout looks down into one of the strangest little canyons in the Southwest. Coal Mine Canyon (Ha Ho No Geh, in Hopi) is a kilometre-wide bowl of badlands eroded into pink, white, and grey clay, with hoodoos and pinnacles that look like a miniature Bryce — and almost nobody around. The colour comes from coal seams interbedded with volcanic ash and Navajo sandstone, mostly oxidised over the millennia.
There are no facilities, no marked trails, and no signage. Park at the small windmill (a pre-WWII Aermotor still in use) on the south side of 264, walk fifty metres to the rim, and pick your way along the edge — the views shift dramatically every few hundred metres. Best in early morning or, especially, on a full-moon night, when the white rock takes on a blue cast. Stay back from the unfenced rim; the rock crumbles.