Glen Lake Rotary Park is an 83 acre recreation area on the northeast edge of Bozeman, and the lake at the middle of it used to be a gravel pit. The site was mined for sand and gravel for decades; when the pit reached groundwater and filled, the result was a clean, steep sided lake with a gravel bottom that the city and the Bozeman Sunrise Rotary Club turned into a park. Locals call the swimming area Bozeman Beach, and for a town without a natural lake in walking distance of downtown, it does a lot of work on a hot afternoon.

The beach is a strip of imported sand on the west shore with a gradual entry into water that gets deep quickly, and there is no lifeguard at any hour. The lake is groundwater fed, which makes it noticeably cold even in August, and clear enough to see the bottom well out from shore. Water temperature in midsummer usually sits somewhere in the 60s, and the hot spell that makes Bozeman residents want to swim is the same hot spell that keeps the lake tolerable. Motors are not allowed, so it is paddleboards, kayaks, floats and swimmers only.

Everything here is free. There is no entrance fee, no parking fee and no reservation system. Facilities are modest: a gravel parking lot off Manley Road, portable toilets, a few picnic tables, and a network of mowed and gravel paths around the water and through the surrounding ponds and wetlands. The city has added benches and shade over time but there is no concession, no rental stand and no potable water, so bring what you need.

The other half of the park is the dog area. Glen Lake holds the largest off leash space in Bozeman, a wide stretch of grass, brush and secondary ponds where dogs can swim and run, and on summer evenings the dog traffic outnumbers the human swimmers. Keep that in mind if your idea of a beach is a quiet one. The swim beach itself has its own rules about dogs, posted at the entrance.

Around the park are the East Gallatin Recreation Area ponds, a trail system that links into Bozeman's larger Main Street to the Mountains network, and good views west and south to the Bridger Range and across the Gallatin Valley. Fishing is allowed with a Montana license; the lake and the adjacent East Gallatin River hold trout, and Montana Fish, Wildlife and Parks stocks water in the area. Downtown Bozeman is about three miles southwest, and the park is a reasonable stop on the way in from the interstate.

One honest note about this listing: Glen Lake is genuinely under photographed. No freely licensed photographs of the beach are available, which is unusual for a park this well used, so the page relies on video and written sources rather than pictures.