This knobby, drooping New Orleans oak is a favorite place both for climbing and for meeting giraffes.

A lush green oasis in the middle of Chicago.

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

Mother Nature outdoes herself with this stunningly beautiful set of caves carved into marble.

A special shop catering to the needs of things that go bump in the night, and also helps kids become writers.

The world's longest known cave system.

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

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

This lab's maddening silence is good for business but bad for sanity.

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

A self-built castle made by a mysterious man.

A huge musical sculpture and other art installations on the National Oceanic and Atmospheric Administration grounds.

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

This upscale streetwear store is hidden behind a fake Snapple machine in the back of a deli.

This cemetery has graves dating back to the 17th century, including the city's oldest carved tombstone and an ominous cryptogram.

A museum dedicated to the history of a terrifying secret police is now held in their former headquarters.

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

Private collection of art inspired by cabinets of curiosity.

One person's lost luggage is another person's treasure.

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

High atop the Eiffel Tower is a small apartment built exclusively to entertain the science elite and make the rest of Paris jealous.

Each year these high desert hills are absolutely covered with poppy flowers in a surreal show of nature.

San Francisco's newly reopened hands-on science museum.

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