Over a thousand feet beneath the Detroit streets is a subterranean metropolis few are allowed to enter.

Visit the site of a subway powered by nothing more than air--and lots of it.

A group of college students hauled a desk up a mountain more than 40 years ago. The notebooks inside have become a makeshift time capsule.

A once-groundbreaking power plant turned into a hotel and mini-museum of archeological and geological wonders.

Take a steam-powered ride straight out of the past on this Appalachian rail line.

This lookout tower built in the 1930s is now an in-demand cabin with what might be the best view of the Seneca State Forest.

This hydraulic power system in London was, at one time, seen as a rival to electricity and the last of its kind to shut down.

Putting the "mod" in "modular" since 2000.

The first geometric self-supporting spiral stairs in Britain are a truly beautiful sight.

Swim or sail to this pie-slinging boat off the coast of St. Thomas.

Dine on ceviche tacos in the sea at this floating restaurant only accessible by boat.

Hike, ski, or snowshoe to a backcountry yurt that serves up gourmet, four-course dinners.

In the 1950s, two women saved this grand theater in the Colorado mountains from demolition.

At one time this small mining village was the highest town in America but now it sits abandoned while the mine churns on.

The skull of the patron saint of lovers lies in the Basilica di Santa Maria in Cosmedin—maybe.

Nature's water park in the Wadi Bani Awf valley is full of pools flanked with cliffs and natural water slides.

The best-preserved beehive tombs in Oman with spectacular backdrop.

Steam engines and conveyor belts are remnants of a genius system left in the middle of the Maine woods.

The world's largest rotating world.

This tiny patch of arid sand sits in one of the greenest states in the United States.

Grapes be damned, this distillery makes wine from apples, blueberries, cranberries, and more.

These light, hollow rolls have been linked to Acadia National Park since the 1890s.

When the town wouldn't allow the fast-food behemoth to build a new restaurant, they put one inside an 1850 home.

Maine's oldest diner also happens to win acclaim for its elevated comfort food.