Where is the world's largest underground salt mine?

On the shores of Lake Huron, in the town of Goderich, Ontario, Canada is the Sifto Salt Mine. This mine is owned by Compass Minerals.

Discovered in 1867, while drilling for oil, a large salt deposit was found and mining began. The mine is 1800 feet below Lake Huron and as much as 2 miles out from the shore. The mine is like a city under the lake and is the same size as the town of Goderich. The annual production of salt is around 9 million tons. Public tours are no longer offered.

The Town of Goderich has been voted as one of the prettiest towns in Ontario. There is a boardwalk and scenic outlook with a beautiful vista of the lake. The public beaches are quite a draw for tourists.