These ominous lava formations were said to be an entrance to the netherworld so of course they inspired a famous metal band.

A decommissioned submarine base makes a great space for graffiti art.

Rusted cars, trucks, and buses form a fascinating collection of Soviet-era machinery.

This former Soviet military base has over 10 original aircraft and an enormous amount of memorabilia on display.

A museum in the building where Nazi Germany signed its surrender tells the story of World War II from the Soviet perspective.

This modern French ossuary contains the jumbled bones of 130,000 WWI soldiers.

This French ghost town from World War II has been left as a memorial to German atrocities during World War II.

Museum dedicated to the terror regimes of Hungary.

Buried five stories underground, this Soviet bunker is packed with gas masks and Cold War paraphernalia.

This striking fort on the Maginot Line looks just as it did after being destroyed in the Fall of France.

This bunker in northern France was built by Nazi German forces with the intention of launching up to 50 V2 rockets at London each day.

After being destroyed by IRA sympathizers, the ruins of this stately Irish manor have sat vacant for decades.

There might not be much left of these Irish ruins, but their linguistic legacy is still going strong.

Once the longest bridge in Ireland, this rusting span sits abandoned and overrun by nature.

An ancient neolithic tomb that only sees the sun twice a year.

A moody and picturesque riverside ruin overgrown with vegetation.

An Iron Age fort on the edge of a seaside cliff offers a glimpse into an ancient, mystical world.

This permanent collection of preserved bodies taken from Irish bogs is one of the leading authorities on such morbid mummies.

This floating garden in the sky is straight out of a fairy tale, but the real thing is nothing short of magical.

Perfectly preserved ancient monastery in an impossibly dramatic location on a rocky island in the Atlantic.

A cableway for car transport.

A line of disused military bunkers built to defend against Nazi invasion lies hidden on the outskirts of the city.

A rooftop restaurant hides in plain sight atop Vienna's Palace of Justice.

The housing complex served as an anti-fascist fortress during the Austrian Civil War.