Hidden beneath the streets of London is a secret subway that only carried mail.

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

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

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

This South London cemetery holds the remains of more than 15,000 people.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

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

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

This odd 1930s shop remains stranded in time and shrouded in mystery.

Dedicated to an "Unknown Man," this grave holds either the remains of a lovelorn suicide or a Cold War spy.

This eccentric cave dwelling is bizarre even by the standards of a subterranean town.

Relics of Australia's convict past, and a modern scene of unimaginable horror.

Rainforest filled with record-holding eucalyptus.

Started nearly 100 years ago, this science experiment just keeps on going, ever so slowly.

Visitors can swim with vicious predators in Crocosaurus Cove's plastic daredevil enclosure.

An opal mining town in the middle of Australia where people live, worship, and shop underground.

A clear example of the process of erosion in action.

A castle hand-built by a Spanish dreamer in the Australian tropical jungle.

A massive stairway that almost wasn't leads to one of Australia's most scenic vistas.

A collection of outdoor mystical statues paying homage to indigenous Australians and ecological stewardship.

An Australian lake whose pink hue defies scientific explanation.

A hugely vast Irish landscape of barren rock that stretches for miles.

A favorite with sightseers, this Norwegian funicular provides easy access to a stunning view of Bergen and its environs.

This religious complex carved into a cliff is steeped in legends of miraculous stags and the Holy Grail.