Secret Swing.

A toxic ghost town sitting atop a massive coal fire.

World's first "penitentiary," meant to be humane, drove men insane.

Series of storm drains connected to a dark urban legend.

The remnants of two World's Fairs are here, complete with a 12-story globe, a mini-Manhattan, and a UFO-shaped pavilion.

The crown jewel of the Queens Museum is a nearly 10,000-square-foot architectural model of the city originally built for the 1964 World's Fair.

Home to the infamous "Typhoid Mary" and the worst loss of life in New York's history prior to September 11, 2001.

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

A graffiti Mecca welcoming artists from around the world.

Ride the subways of yesteryear.

Three-story slide through the New Museum.

The ghostly remains of an accidental sea.

The abandoned zoo enclosures offer a perfect place to experience the other side of the bars.

Towering basalt columns, a creation of fire and ice.

Haunting and beautiful trees, doomed to die.

Home to the "Circus" trees created by Axel Erlandson.

The largest drain hole in the world.

Inside an old airplane hangar, friends and strangers alike play on a massive trampoline.

An optical illusion found amid a logged redwood forest.

Canyon walls shrouded in ferns.

A heavenly experience, right here on Terra Firma.

Shoreline strewn with the remains of ghostly fallen trees.

Stroll through a wonderland of stupendous moss-covered trees.

A walk through the historic city center, under the streets of Seattle.