The Mackinac Bridge, nicknamed Mighty Mac, is the world's third-longest suspension bridge. It links Mackinaw City on the lower peninsula to St. Ignace on the upper. Its deck is 200 feet above the water, and it can sway as much as 11 feet in either direction.

There's a reason why the speed limit on the bridge is a relatively slow 45 miles per hour—anything more, or even that, feels too fast with the wind blowing and the see-through deck. (Yes, it's true: A car did once blow off. A Yugo, but a car nonetheless.) Freaked out? Ask, and a member of the bridge crew will drive for you.

An annual bridge walk draws thousands to stroll across the structure, with shuttles providing a ride back.