Once the tallest building in the world and the site of “the highest dinner ever held in New York” this building now holds the most expensive penthouse in the city.

The largest self-built castle in the U.S., six decades in the making.

An unfinished revolving restaurant on a church campus towers over suburban Northeast Ohio

An organ located deep within a cave, whose "pipes" are the geological features of the cave itself.

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

This functioning mill was built in the 1970s using parts from several other West Virginia mills.

A former mental hospital founded in the 1930s by a eugenicist who advocated for the forced sterilization of patients.

This rural community has attracted both scientists and techno-refugees due to its federally-mandated lack of technology.

The world's largest fully steerable radio telescope.

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

A sacred site for Native Americans surveyed by George Washington and owned by both King George III and Thomas Jefferson.

A steel skeleton is all that exists of what is supposed to be a replica of Noah's Ark

Despite violent work crews and massive delays this abandoned canal tunnel was built to last into the modern day.

This abandoned dream castle and its cemetery look out over the city that once inspired their creation.

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.

World-famous, Pink's still manages to keep its prized cult fetish status.

The fifth-longest suspension bridge the world, connecting one Michigan peninsula to another.

Island where motor vehicles are banned -- home to the only carless highway in the United States.

This nearly 200-foot tall limestone stack offers visitors amazing views and a chance to meet Paul Bunyan and Babe the Blue Ox.

For over 100 years, this Indiana town has had a tree growing out the top of the local courthouse.

An important Mayan religious and trading center dating back to 200 BC.

These sub-farmland caves are home to a majestic stalactite known as the "Crystal King."

This hidden sculpture garden full of Wild West art is one of San Antonio's best-kept secrets.

Craggy concrete faces are hidden in the walls of this artificial cave along the San Antonio River.