The world's longest known cave system.

Take a drunken tour inside the world's largest known geode.

Philadelphia boasts one of the best — and most often overlooked — traditional Japanese gardens in North America.

Explore the largest pure gypsum deposit in the world, and go dune sledding while you're at it.

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

One man has carved a number of natural New Mexico caves into psychedelic sandstone temples.

Dramatic river bend surrounds a natural red-rocked pedestal.

America's most famous museum of medical oddities is home to the remains of Albert Einstein's brain.

Rippling sand dunes frozen in the Arizona rock.

A fiery crater has been burning in the Karakum Desert since 1971.

A bizarre house filled with an astounding array of collections.

12,000 sq. ft. museum tracing erotic art from antiquity to modern times.

The only swimming pool listed on the National Register of Historic Places is emptied and refilled each day with naturally filtered water.

A turn-of-the-century architectural marvel built on healing mineral springs and salt licks.

The longest navigable underground river in the United States is home to countless blind and albino animals.

Working compound meant to allow visitors to reclaim the values and traditions of the past.

A giant 400-acre preserve in North Florida for displaced wolves.

St Bernard de Clairvaux Episcopal Church, better known as one of the oldest European buildings in the Western Hemisphere.

The largest retailer of seashells in the world.

In the depths of the Everglades, one man has dedicated his life to studying the elusive Skunk Ape.

Welcome to old Florida, where a 1940s mermaid show is still enchanting visitors.

Ancient church constructed with a special wood that preserves prints from the past.

Florida's first suspension bridge.

Former utopian colony based on the belief that the universe exists in a hollow sphere.