(RNS) Earlier this month we learned that Washington, D.C., police had charged a prominent rabbi with spying on naked women at his synagogue’s mikvah. So what is a mikvah, anyway, and does it have anything to do with sex? What’s a mikvah? A mikvah is a pool of water — some of it from a natural source — in which observant married Jewish women are required to dip once a month, seven days after the end of their menstrual cycle.