Bison Trail aka Dog Run Hollow is one of the best trail running loops in Oklahoma. Located in the Wichita Mountains Wildlife Refuge, this trail has multiple access points. The trail itself is good, relatively flat and easy to follow. The western end of the loop passes by the 40 Foot Hole canyon, which has a big (rain-dependent) waterfall. Springtime brings lots of wildflowers. As always, be snake-aware in the Wichitas.