Hershel Shanks

The ritual bath. A stone staircase leads down to a mikveh, a pool for ritual immersion. Jewish law requires that water in a mikveh must be standing rainwater or water that has flowed naturally—not drawn or carried in any way. To comply with this law, mikva’ot (plural) were sometimes built with a second pool, called an otzar (reserve), that held undrawn water. A small channel connected the two pools; contact by the water in the otzar with drawn water in the immersion pool rendered the latter fit for use in ritual purification.