Amidst medieval and baroque buildings, five human-sized gherkins stand tall.

An ornate private entrance to the Vienna subway built specifically for the emperor.

"World machine" built by an untrained Austrian farmer.

The medieval network of canals hidden underneath the city is opened to explorers each year.

The world's oldest known salt mine.

American soldiers discovered Europe's best one-liner at the end of World War II.

Resting in the middle of an Austrian river, this sci-fi "island" lets people cross in neon style.

The largest ice cave in the world is thought to be the entrance to hell according to Austrian legend.

A centuries old castle atop a dormant volcano houses museums devoted to both women and witches.

Each year melting snow turns these Austrian hiking trails into scuba zones.

Terrifically morbid cemetary and site of famous Paracelsus' grave.

Apartment complexes built into huge repurposed natural gas tanks.

Inside the corridors of this flea market, visitors are sure to find some obscure and odd treasures.

Vienna's underworld of tunnels and subterranean rivers made an iconic appearance in a 1949 Orson Welles film.

Trick water gardens from 1619 featuring a 200 piece mechanical theater powered by water.

An artsy hidden staircase leads to breathtaking views of San Francisco.

The Metropolitan Police refurbished the blue box (perhaps not coincidentally) the same year "Doctor Who" returned to TV screens.

After nearly 60 years, there's still a bear at Paddington Station looking for help.

One part local history, 99 parts gruesome haunted house.

This 1920s Dutch barge is now a floating bookstore.

Eighty million natural history specimens call this gargantuan museum home.

Banksy gives themself artistic license with this piece of London street art.

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

The popularity of Sherlock Holmes led to the creation of his fictional address, turning the orderly London street numbers askew.