8. Great Bear Lake
Great Bear, 12,000 square miles of frigid water and ice, is the largest lake entirely within Canada. It's located in the nation's Northwest Territories, east of Alaska. The Arctic Circle runs through the northern part of the irregularly shaped lake, which has five distinct "arms." Great Bear is iced over for all but about four months of the year.
Great Bear is largely pristine, but it's had a spotty past. The Canadian government mined uranium there in the early part of the 20th century and dumped some 750,000 tons of uranium-tinged mining waste into Great Bear. Now, the area is being explored for oil reserves.