The lake shape resembles a slight figure eight with several distinct areas. South of the figure eight portion of the lake lies Bean Lake State natural area which is a protected marsh. Part of the south western part of the figure eight is usually covered in tall aquatic vegetation that reach out of the water. In the north western portion of the figure eight there is a sand bar which often has boats anchored and is swimming accessible.
The Glacial Drumlin State Trail[2] runs across an old rail road bridge across the southern portion of the lake. The trail separates the lake from the marsh area to the south of the lake.
Pyramid claims
Rock Lake is perhaps most famous for its underwater rock piles frequently claimed to be pyramids built by the Mississippian culture at a time when water levels were much lower.[3]
The waters of Rock Lake have been referred to as "Tyranena", (Tee-ruh-nay-nuh). That name has persisted in the area and is used by businesses, road names, and a park that is on the lake.
Beaches
There are two public beaches, Bartel's beach[5] and Sandy Beach;[6] both are located in the south eastern portion of the lake.
Fishing
Pike, smallmouth bass, largemouth bass, rock bass, pumpkinseed, bluegill, sunfish and walleye can be found in Rock Lake.