In Northern Minnesota there is a lake, Cass Lake. There is an island in that lake called Star Island. On that island there is a lake - Lake Windigo. It is the only lake within a lake in the northern hemisphere (so I've read).

My daughter attends a camp which is located on Star Island - I actually went there too, about 25 years ago.

http://www.casslakelodge.com/casslake.html

The campers speak of the "Windigo Monster" which supposedly lives in the lake.    I don't think it is related to the Windigo this thread refers to ...

fwiw