Bartel's Beach is a two-acre city park and swimming beach on the east shore of Rock Lake in Lake Mills, Wisconsin, run by the City of Lake Mills Parks and Forestry Department. The city lists it at 217 S Ferry Drive. Older maps and the federal place-name database still call the spot Lakeside Park, but locals and the city both use the Bartel name. Augie Bartel built the boathouse next door in 1931, and for decades swimmers checked their street clothes there in numbered baskets. Rock Lake is a 1,365-acre lake whose shoreline is split between the City and the Town of Lake Mills, and this is one of only two public beaches on it. The other is Sandy Beach at the south end.

The park sits a few blocks south and west of downtown and Commons Park. From Main Street, follow Ferry Drive along the lakeshore to the beach. Parking is a small lot and street spaces along S Ferry Drive, and they fill on hot weekends. You can also walk in: a lakeside path starts behind the fire station on Main Street and follows the shore to the beach, though it can be muddy after rain. A pedestrian bridge crosses the Mill Pond outlet channel, which cuts through the park on its way into the lake.

The city describes the park as a beach with a swimming area, and the swim zone is marked off from the boats and personal watercraft that use the rest of the lake. Visitors describe a sandy bottom that deepens gradually, which lets small kids wade near shore, and Rock Lake is known locally for clear water. The lake warms through June, and July and August are the reliable swimming months. The city does not list lifeguards for Bartel's Beach, so plan on swimming at your own risk and keep a close eye on children near the edge of the swim area.

Bartel's Beach is free. The city's parks directory lists no admission, parking fee or permit for it. The $12 daily parking fee and resident permit program you may read about apply only to Sandy Beach Park, and the city's parking page names Sandy Beach alone. The local chamber of commerce lists Bartel's Beach among the free things to do in town. The city does not post separate swim hours for the beach, so follow whatever is on the signs at the park.

Water quality is the main thing to check before you go. Each summer the city samples Bartel's Beach weekly, along with Tyranena Park and two spots at Sandy Beach, and sends the samples to the Wisconsin State Laboratory of Hygiene. Results usually come back within a day as Open, Advisory or Closed, and the city posts the current status near the top of its website and in an email to subscribers. A positive test triggers daily sampling until levels drop. Bartel's Beach has been closed for high E. coli in recent summers, generally for several days at a time before reopening on a clean retest, so check the city site on the morning you plan to swim.

Beyond the beach, the city lists picnic areas, grills, restrooms, a playground, shoreline fishing and a short nature trail in the park. The Bartel's Landing boathouse just north of the beach, rebuilt after a 2002 fire, is private property. Its owners reopened a concession stand for beachgoers there in 2017 for the first time since the late 1980s; its hours are up to them. Downtown restaurants and the summer concerts in Commons Park are a short walk away.