One Of Minnesota's Deepest Lakes Is A Former Mine With Scuba Diving And Sunny Swim Beaches

Known as the Land of 10,000 Lakes, Minnesota offers endless opportunities for getting out on the water and Portsmouth Mine Lake is one such spot. This stunning lake, located about 130 miles north of Minneapolis in Crosby, Minnesota, isn't really a lake at all but rather a former iron ore mine that was filled in with water. It's one of several pit mine lakes in the Cuyuna Country State Recreation Area, which is particularly famous for its 50 miles of mountain bike trails, but also popular for many other outdoor activities including hiking, fishing, kayaking, canoeing, swimming, and even scuba diving.  

At nearly 400 feet deep, Portsmouth Mine Lake — sometimes called the Portsmouth Mine Pit — is one of Minnesota's deepest inland lakes. Around the lake, there's a great public beach for swimming, although be conscious of the steep drop-off that can quickly take you from the shallow waters near the shore into water that is hundreds of feet deep. The water of the lake is remarkably clear, providing incredible views far down into the depths of the pit mine. With no motorized boats allowed on the lake, it's a calm, peaceful place to swim or paddle.

Portsmouth Mine Lake is about a five-minute drive from downtown Crosby, off Highway 30. From there, you'll follow an unpaved road until you come to a campground on the northwest shore of the lake, which is also where you'll find the parking lot. Continue on a bit further to get to the swimming beach. Minnesota is a great stop on any Midwest road trip, but if you're flying to the Land of 10,000 Lakes, you'll need to rent a car to visit the Cuyuna Country State Recreation Area and Portsmouth Mine Lake as public transportation options are extremely limited. From the Minneapolis-St. Paul International Airport, it's between two and three hours to Portsmouth Mine Lake.

Minnesota may not come to mind as one of the world's best scuba diving destinations, like this Malaysian island, but its many lakes provide excellent scuba diving for beginners and advanced divers alike. Iron pit mines like Portsmouth Mine Lake are great for wall diving, and the lake's deep, crystal clear waters provide up to 50 feet of visibility. Divers can explore mine shafts, walls, and shelves and observe marine life including fish like trout, bass, and northern pike. The Minnesota School of Diving in nearby Brainerd hosts group dives several days a week at Portsmouth Pit Mine Lake and other pit mine lakes in the Cuyuna area from May through October for certified divers. You can also rent equipment from their shop and dive on your own — just remember to avoid flying right after scuba diving.

Wondering where to stay? The Portsmouth campground on the lake has 29 sites you can reserve in advance. Furthermore, the towns of Crosby and Ironton also have plenty of other lodging options from traditional hotels and motels to yurts and camper cabins. Or, head a little further afield to Nisswa, another cozy lake city in Minnesota for nature activities and outdoor recreation.