Rock Lake in Lake Mills is the cleanest lake in southern Wisconsin because it's spring fed, but it's even more famous for the rock piles, or pyramids, reportedly found on the lake's bottom. Legend has it that in 1066, after suffering a long and terrible drought, Aztec Indians appealed to their gods for help by building and using sacrificial pyramids. In answer to their prayers, great waters soon covered the pyramids and created the lake the Indians came to call Tyranena, meaning "sparkling waters." In 1836, white settlers renamed it Rock Lake, and today it is a pleasant spot for recreation, with a nice sandy beach.