A three-story copper skybridge connects two Manhattan buildings with Art Deco luxury.

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

A series of haunting wooden totems are hidden in the woods surrounding a German environmental center.

This natural history museum houses one of the world's largest rat kings, a terrifying jumble of tangled rodents.

An acoustic anomaly with a mysterious cause.

This whimsical group of statues is a favorite of children who love to climb all over Lewis Carroll's beloved characters.

Hidden in Central Park's Ramble is a troublesome cave buried just beneath the surface.

Carved by a waterfall in a hard-to-reach rock formation, this heart-shaped rock has inspired romantics for decades.

A surprisingly detailed model of one of the most powerful telescopes in the world.

A tunnel once abandoned now thrives with graffiti art as an off-limits makeshift gallery.

This modern antique shop is a museum for 1980's Saturday morning cartoon culture.

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

A modernist landscape of water and sci-fi concrete.

The land is full of geologic eye candy, such as otherworldly spires, mushroom-shaped hoodoos, and prehistoric fossils.

The hike through a narrow river flanked by the 2,000-foot-tall walls of Zion Canyon is one of the best in the world.

A self-built castle made by a mysterious man.

The magic's in the hole!

Giant busts of 42 U.S. presidents are sitting in a field in Virginia.

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

This incredible collection of vintage pinball machines can be played at 25 cents a pop.

A breathtaking array of ancient Pueblo structures and artifacts counterintuitively preserved by neglect.

The seawater playground of gilded-era San Francisco burned to the ground in 1966.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

Seemingly grown on some other world, these New Mexico rock formations look like a disused science fiction set.