This hidden corner of Denver has a proud history of being the best place to test the waters. Grant-Frontier Park commemorates the alleged location of Montana City, the first settlement established by pioneers on the South Platte River a year before the city of Denver. The width of the river narrows just north of the park's foot bridge, and the bike path is routed away from the river, leaving a stretch of river bank perfect for reenacting the pioneer peel. In the summer, the slow-moving shallow water is quickly warmed by the hot sun. A trek through the thick undergrowth is a must for the more secluded wallowing spots away from hostile witnesses and bored park police. Also, it's probably best to keep your face out of the river water, as the Englewood city sewage treatment plant is less than a mile upstream. As all skinny-dippers and pioneers know, keeping your head up and your eyes and ears open is the smart way to keep your ass out of hot water.