Black Rock Hot Springs is a small thermal spring system west of Arroyo Hondo, New Mexico, beside the Rio Grandé. Water rises from a cluster of basalt boulders at the river’s edge and, when the river is low, feeds several small primitive soaking pools lined with rock. The largest pool has a gravel bottom, is about four feet deep, and measures roughly twelve feet across. Water emerges at about 106 °F at the source, but the pools are cooler because they mix with river water; the largest is about 98 °F. The river sometimes washes out the pools, and the site has never been commercially developed.