The history of this land’s formation goes back billions of years, but Detroit is young in geological terms. There once was no human life here — just ice. 

10,000 years ago, ice more than a mile thick covered Michigan. The slow scraping of four major glacial advances and retreats sculpted the Great Lakes, our rivers and streams, and the distinctive contours of the state's upper and lower peninsulas.

Even today, 1200 feet below the city’s streets, there are vast, 400-million-year-old salt deposits left behind by a long-vanished sea. The salt is mined along 100 miles of underground roads — and used to melt the ice from our modern winter storms.