This state park was once an important Native American cermonial center.

This historic park site contains the last remnants of a once bustling canal system.

This pre-Revolutionary War grist mill ground corn and flour for soldiers in seven American wars.

The famed architect designed this Minnesota gas station of the future with a lookout tower.

Shaped like a big top tent, this memorial honors the victims of a terrible train wreck.

These tourist trap caverns are said to be the former home of a legendary Pennsylvania Hermit.

One man's ambition created this psychedelic log home.

A key producer of charcoal iron in the early 1800s, the structure still stands today.

The Grand Ole Opry's big voice came from a small home in rural Virginia where she was eventually buried.

Dr. Strangelove-esque tours reveal the inside a bunker once reserved for Stalin himself.

Once the future of underwater combat, this old sub is now open for visitors to muck around in.

Hidden inside this Arizona fast food franchise is an in-depth exhibit on the famed WWII counterintelligence program.

This unique railroad museum secretly contains the history of Poland rebuilding itself from the inside-out.

Once the "Eighth Wonder of the World," this iron railroad bridge was decimated by a tornado.

This crumbling UFO is one of only a few remaining "moveable ski chalets" of its kind.

A rock outcropping left by a glacier that made itself useful throughout the centuries.

These mysterious petroglyphs in Vermont reflect a troubled history in the treatment of Native American culture.

There aren't too many operational funiculars around, but Pittsburgh has two!

A graveyard of bathyspheres and diving bells paints a weirdly accurate account of ocean exploration's rickety history.

Hidden away in the city of Madison, Wisconsin is a nearly forgotten home that Frank Lloyd Wright built for a childhood friend.

One of Frank Lloyd Wright's final works was this UFO church.

Early prototype for Frank Lloyd Wright's Guggenheim.

This architectural triumph is the only Frank Lloyd Wright house in Alabama.

A preserve with 75,000 ancient drawings remains the realm of public – not just scientific – exploration.