A recently abandoned psych ward at the end of Sanatorium Road.

Once the world's largest reinforced concrete structure, this abandoned bridge now beckons urban explorers.

Now abandoned, the first public health hospital in the U.S. saw more than one million immigrants from around the world.

New Jersey's last historic covered bridge was rebuilt from pieces of the original 19th-century structure.

Hidden in plain sight on the Hudson River is an abandoned train station where nature has taken over.

Between Neo-Pagans and Neo-Nazis, these strange rock formations have a curious cult following and a very strange history.

This mysterious artificial cave has long puzzled New Englanders.

Quirky castle designed by the American actor best known for portraying Sherlock Holmes on stage.

The kind of mixed-up place that drives archaeologists crazy.

Few of the many visitors to this resort town know of its hidden Maya ruins.

A Neolithic burial site erected around 3000 BC.

The castle where Martin Luther secretly translated the New Testament from Greek to German while in hiding.

Living trees form the structure of an open-air palace.

The 3,600-year-old archeological sensation is considered to be the oldest representation of the cosmos.

A Neolithic celestial calendar standing in a nondescript wheat field.

A statue of the legendary Celtic warrior queen who fought the Roman invaders stands in one of the cities she once destroyed.

One of the American Southwest's most extensive collections of Navajo rock art.

A simple plaque remembers an act of WWI terrorism that obliterated an island and forever scarred the Statue of Liberty.

Decades after testing the polio vaccine on unwitting patients, this historic mental hospital sits in ruin.

Seven golden statues rise into the sky from sculptor Victor Victori's New Jersey front lawn.

Mysterious rocks that ring musically when struck.

A world-class collection of mechanical musical instruments and automata.

This tiny New Jersey village has lived many lives but seems determined to remain a ghost town.

The remains of the furnace and iron works that produced the massive Hudson River Chain still stand in the woods of New York.