Huge concrete structures designed as an early warning system for Britain to detect enemy aircraft.

This Belgian theme park began as a refuge for bored church children and was closed down when a boy lost an arm.

This once-grandiose behemoth of a monument from the socialist era now sits quiet and closed up.

The mouldering remains of a disgraced British children's icon are hidden in the brush of a public park.

Budapest's Communist-era statues, banished to the suburbs.

London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.

A former imperial sea-fortress and Soviet prison.

Terrifying derelict military hospital once housed a recuperating Hitler.

An abandoned NSA listening post on Berlin's "Devil's Mountain."

The curios of pharmacist and collector Henry Wellcome.

An eerie, derelict amusement park in Berlin.

One of the first big sculptures anywhere in Australia.

This ghost town in Belgium will lose its street art when it ceases to exist.

A church of bones, decorated with 40,000 human skeletons.

An abandoned saucer-shaped monument in the Bulgarian mountains.

The decaying ruins of Wales' first asylum for the mentally ill.

This hospital once pioneered the use of electroencephalograms, but fell into maltreatment, abuse, and eventual abandonment.

This attraction was abandoned after the Chernobyl disaster.

A historic arboretum and non-conformist, non-denominational park cemetery.

A vast overgrown cemetery, once known as one of London's "Magnificent Seven."

The hidden "ballroom" under a mansion lake was built by a criminal who ate a cyanide pill during his trial.