The final resting place of up to 6,000 Confederate soldiers, the largest mass grave in the Western Hemisphere.

The final resting place of the world's first nuclear reactor.

First known as the "Sample House," this construction mash-up was meant to be a living catalogue of building styles.

Tombstones carved to look like tree trunks are used for multiple generations of family members.

A hidden network of subterranean passageways lies tangled beneath Indianapolis' bustling City Market.

Built in 1869, this now-retired structure looks more like a medieval fortress than a county lock-up.

An eerie, decaying ghost town destined to fade into the forest.

The ruins of an abandoned 18th-century town that is slowly being reclaimed by the forest.

The eerie ruins of a remote abandoned hamlet said to be founded by the survivors of a shipwreck.

A mining town, now abandoned, was built in a canyon so narrow that the railroad ran right through the hotel lobby.

A nearly abandoned 19th-century town on the Palouse.

The scant remains of this flooded historic village can be explored in one of the most remote areas of the Great Smokies.

In the bowels of a 19th-century brewery lurks a fine-dining restaurant offering an array of themed feasts.

These 12th-century catacombs carved into a mountainside were a place of mysticism and Christian hermitages.

This ossuary is more than five centuries old and is heralded as one of the finest in Switzerland.

A hidden gem in the middle of the city's infamous Jewelry Quarter.

This small Newfoundland town has declared itself the “Root Cellar Capital of the World.”

The walls of a colonial-era fort encircle a small, tropical assortment of plant life.

This New York estate was designed to resemble a medieval Scottish castle.

The mysterious, fantastical woodland inspiration for "The Lord of the Rings."

An artsy hidden staircase leads to breathtaking views of San Francisco.