Rock Lake is a 1365 acre lake located in Jefferson County adjacent to the Lake Mills Wildlife Area and the Bean Lake State Natural Area. It has a maximum depth of 60 feet and contains large populations of a variety of fish. Visitors have access to the lake from four public boat landings. The northern shore contains sandy beaches where swimming is available and boating is popular and the southern shore contains emergent aquatic vegetation. Rock Lake is famous for its underwater pyramids which are believed to have been built by Aztalan natives long ago. The views and scenery are very beautiful.