When is a lake not a lake? When it’s a river. Medicine Lake is a geologic anomaly: though it looks like a long—4.3 mi (7 km)—and relatively shallow lake, it’s actually an area of the Maligne River. During times of glacial melt during the summer, the water backs up and forms the “lake” until it can slowly drain underground again through a series of sinkholes.
Aboriginal people called the lake Medicine Lake because of its incredible disappearing trick, but visitors these days are inspired by the opportunities for wildlife viewing of large mammals like bear, deer, moose and caribou. Fly-fishing is another popular pastime due to the proliferations of trout, but be prepared: Medicine Lake disappears in the fall and winter months, becoming a mudflat.