Under a glass sidewalk lie the remains of some of Manhattan's oldest buildings.

A pair of slides and a tree-lined stair corridor have been an urban oasis for nearly 40 years.

An underwater city for the dead.

Where manatees are the snowbird vacationers in these balmy Florida springs.

A dilapidated dock tells the story of Titanic's missed arrival.

Possibly the most beautiful carillon in the world, set atop Iron Mountain in Florida.

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

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

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.

The unique waterfall in Iceland's south features a backdrop of geometric black lava columns.

A trash dump made beautiful by nature's power.

Mysterious rocks that ring musically when struck.

The deepest lake in the United States, and once the site of epic destruction that lives on in legends.

This 1,300 year old monastery built atop a single rock was once only accessible depending on the whims of the tide.

The United States Capitol's former columns still stand.

The sign at the garden gate reads: "These Plants Can Kill."

Where America's first doomsday cult awaited the end of the world.

The intricate stonework of Machu Picchu serves as a testament to Incan engineers.

Here, at the "world's longest art gallery," you'll find forty miles of ancient petroglyphs and pictographs.

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

Enormous lake at the bottom of a unique cave system.

The fairy tale castle of the "fairy-tale king."

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

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