Decommissioned experimental solar facilities that pioneered solar energy technology.

Don't blink or you'll miss it.

This golf ball–shaped former desert real estate office now houses a UFO museum.

The headquarters of a secretive order is also a beautifully-designed park.

An extensive collection of ancient Egyptian artifacts and mummies.

The remains of a chapel created for convenience.

The only remnant of a small mining town is an abandoned railroad tunnel that is steeped in ghostly lore.

This replica of the Greek structure is in the heart of Nashville.

A perfect circle of 24 mysterious holes dates back to prehistoric times.

I-95's Tijuana-style celebration of kitsch at the Carolina border.

The Denver airport is guarded by a 32-foot-tall sculpture of a demonic horse.

Once connected to the outside world by a single train track, this ghost town is looked after by the National Park Service.

Frank Lloyd Wright’s most iconic home dangles over a Pennsylvania waterfall.

A restored Pittsburgh house of God has been converted to a marvelous house of suds.

The United States’s oldest funicular railway glides up and down a steep Pittsburgh street.

The largest ancient burial mound in Ohio.

Georges Seurat’s pointillist masterpiece has been recreated in Ohio in topiary form.

The second-longest continuous wall on the planet protects a hidden secret in the deserts of India.

A blooming house of worship for the masses.

More than half of this Indian palace is drowned but it looks all the more spectacular for it.

The 953 windows undoubtedly make this the world's most beautiful screened porch.

The world's second-largest sundial, made entirely out of stone.

A tiny piece of the Moon is embedded in this stained glass masterpiece.

The sci-fi villain is a little-known inhabitant of the U.S. capital's largest cathedral.