Beaver Dam, Maryland - Wikipedia
https://en.wikipedia.org/wiki/Beaver_Dam,_MarylandBeaver Dam is a flooded marble quarry in Cockeysville, MD that has been used as a swimming location since the 1930s. Currently, a 30-acre swim club is located there with two swimming pools, a volleyball court, picnic tables and grills, a creek, and snack house. The 200 foot deep freshwater quarry has floating platforms, two rolling logs, diving and jumping platforms, and a rope swing.