Ice Road to Madeline Island
This road across the Lake Superior ice links Bayfield, Wisconsin to Madeline Island in the Apostle Island National Lakeshore. Only exists in the deep freeze of winter - usually there is a car ferry.
I estimate it to be 2-3 miles long, and while you drive directly on the ice surface, it did not feel slippery at 15 mph.
Dawn, February 9, 2014. I think it was about -11 below zero F.