This ancient Hawaiian henge may have been an early star chart.

This ruined fort and statue are a testament to the last king of Kaua‘i’s savvy diplomacy skills, which briefly brought Russians to Hawai‘i.

Submerged lava formations create incredible waterworks.

The only royal palace on U.S. soil has been a territorial capitol, a military headquarters, and a prison for a queen.

This 11th-century structure is one of the oldest churches in Romania.

Check out engineering marvels of the past at this unintentionally retrofuturist museum.

This bone-filled cave got its name after they found 140 bear skeletons inside.

Conspiracy theories and occult legends surround this mysterious natural rock formation.

The legendary cliffside castle of three-time Voivode of Wallachia, Vlad the Impaler.

A subterranean ice warehouse that has lain hidden beneath central London for over a century is now open to the public.

This foolish Victorian sea fort was converted to a deluxe hotel.

The church is gone, but the graves and legends remain.

Once home to over 8,000 exiled Hawaiians suffering from Hansen's Disease.

Decommissioned NYC subway cars are dumped into the ocean to create this underwater wildlife habitat.

The historic home still shows the scars from a little run-in with the British in 1813.

A wunderkammer hidden on the top floor of the Hartford statehouse.

A mysterious air force base built to resemble a Long Island fishing village.

One-layer pyramid in Indiana.

Civil War Fort on an island in the Boston Harbor.

The ghostly remains of an accidental sea.

Remants of foundations, streets, and streetcar tracks inhabit the cliffs where a landslide occurred in 1929.

Remains of a Greek freighter trapped off of Rocky Point in 1961.

Ornate "Renaissance Revival" style building.

Witness to many historic moments in early Texas history.