Odd outsider art installations surround a Gold Rush-era ghost town.

Hollowed out cedar log tubs set in an ancient towering forest.

A modernist landscape of water and sci-fi concrete.

Frank Lloyd Wright's most iconic home dangles over a Pennsylvania waterfall.

An underwater city for the dead.

Read a book next to a Midtown waterfall.

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

Bigfoot prints, Feejee mermaids, and haunted dolls on display in a tiny North Carolina town.

The "Seinfeld" diner.

This abandoned amusement park was built on a site with a dark history.

A beautiful 62-acre Catholic shrine and botanical garden.

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

Just your average Marie Antoinette–themed speakeasy in an abandoned 19th-century subway tunnel.

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

Enormous lake at the bottom of a unique cave system.

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

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

Try not to get slimed in Tribeca.

These remote Florida islands have a history of sea turtles and sunken treasures, and one of the world's largest coastal brick fortresses.

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

A crumbling hospital from the 1850s on Roosevelt Island.

America's first public lending library began with a gift from Benjamin Franklin.

This historic Victorian mansion is allegedly so haunted that a signed waiver is required to enter.

Historic seaside park featuring explorable, abandoned military structures.