This magnificent Cincinnati graveyard is also a popular public park.

This cemetery has graves dating back to the 17th century, including the city's oldest carved tombstone and an ominous cryptogram.

A crumbling hospital from the 1850s on Roosevelt Island.

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

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

The remains of the second-oldest zoo in Europe can be seen within these library gardens.

This abandoned bridge to nowhere stands secluded in the woods of a Cleveland suburb.

Quite possibly the last cross all humans will ever see.

Toxic waste disaster that founded the Superfund program.

Madrid's romantically ornate crystal palace has been offering shelter to plants and art for over a century.

An ancient Egyptian temple in the middle of Madrid, Spain.

The site of the famous Nazi book burning campaign of 1933 remembers its "Night of Shame".

A monument to the man who almost killed Hitler.

The most visited, and possibly most controversial, museum in Germany.

A fascinating insight into daily life in the Eastern Bloc.

The bunker where Hitler took his own life is hidden under this deliberately ordinary parking lot.

Thousands of coffin-like pillars make up this controversial Holocaust memorial.

The one-time watch house for incoming ships at the Golden Gate now stands abandoned and hidden in trees.

A walk-in working camera obscura produces 360-degree live images of the San Francisco coast.

The seawater playground of gilded-era San Francisco burned to the ground in 1966.

Church built on the site where the last tsar of Russia and his family were killed.

A subterranean house of worship carved right out of the bedrock.

Architecturally stunning library serves as the hub of Finnish scholarly life and culture.

Cleveland's giant "free" stamp is a nod to the Civil War, but was misinterpreted for years.