A decaying, yet still functioning, work of communist architecture.

This massive concrete sculpture is said to be the heaviest communist monument on Earth.

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

Outstanding, eerie frescoes and decorations fill this 19th-century monastery.

This symbol of Yugoslav liberation decorated with 620 carved heads of mythical creatures is now a forlorn relic of another time.

A forgotten and crumbling Yugoslav monument to the victims of fascism.

This stunning, out-of-the-way Croatian monument commemorates a community's uprising against occupying fascist forces.

Croatia's towering concrete blossom grows from the site of a World War II concentration camp.

A tower marking the spot where Yugoslavia began its resistance against the invading Nazis stands neglected, but not quite forgotten.

Take respite inside this jaw-dropping church while climbing the volcano where Georgia's Prometheus was once chained.

These Stalin-era industrial 'death traps' hang lifeless above the city

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

One of the few remaining casualties of the London Blitz, this destroyed church has become an enchanting public garden.

This shop and gallery is a modern-day cabinet of curiosities, unassumingly positioned along an urban thoroughfare.

This churchyard arbor is surrounded by hundreds of gravestones placed there by author Thomas Hardy.

Winding paths and ramshackle mausoleums in the oldest "park cemetery" in London.

Eighty million natural history specimens call this gargantuan museum home.

The only university zoological museum in London houses extinct animals, bizarre natural history specimens, and a Micrarium of microscopic creatures.

One part local history, 99 parts gruesome haunted house.

A 1,215-foot tunnel transports pedestrians beneath the River Thames.

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

A hands-off space for graffiti artists to hone and display their skills.

Catacombs turned marketplace.

The anatomical-pathological collection of a man who changed surgery.