The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

Hear the quietest sound from across the dome.

The most loyal of little dogs, or a Victorian era publicity stunt?

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

The world's longest known cave system.

Giant, natural amphitheaters made of delicate geological formations called "hoodoos."

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

Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.

Home to items never before seen by the public.

A bizarre house filled with an astounding array of collections.

One of the Seven Wonders of the Modern World holds the world's tallest metal staircase.

Strange red rock formations that have been attributed to a higher power for hundreds of years.

High on a hill overlooking Los Angeles lives a world famous, high power conical Tesla Coil.

A beautiful geyser under environmental threat.

See massive fossils that are over 200 million years old in northeastern Arizona.

Home to the largest urban bat colony in North America, estimated at 1.5 million bats.

A monument celebrating the idea of reaching inaccessible places.

This 4,000-foot-diameter hole is touted as "the most well known, best preserved meteorite crater on Earth."

The ancient dwellings of the Puebloans, located in the cliffs of majestic mesas.

The twin towers in this Chicago fountain use 50 foot tall video screens to spit on people.

This historic address is home to the beloved ball and is an almost totally empty building among the most expensive real estate in the world.

One of nature's most well-scheduled phenomenons resides in Wyoming's Yellowstone National Park.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

A former waterfront market is now in the center of town due to some interesting Boston engineering.