The hidden lair of an alchemist rediscovered in a 2002 flood.

Macabre astrological automaton clock dating to the late 1400s.

A Jenga-style cylindrical tower of books that appears to go on forever.

In the middle of a Vienna square, Roman ruins dating back some 2,000 years are on display.

Along the edge of this fountain are 365 smaller fountains that represent the days of the year.

A magnificent collection of imperial armor and weaponry.

A patriotic medieval knight in driven-nail armor raised money for widows and orphans of WWI.

Vienna's diversity-themed traffic lights were inspired by the Eurovision Song Contest.

Giant WWII fortresses that fired 8,000 rounds a minute, now home to thousands of pigeons.

Legends surround an ancient tree trunk riddled with nails for good luck.

Baroque celebration of the end of the Great Plague of Vienna.

The topiary maze at the Habsburg hunting lodge.

The oldest volcanology research center in the world.

The Vatican's secret porn-festooned bathroom was painted in erotic murals by one of the greatest artists of the Renaissance.

The Pope’s secret escape route.

The first island in the world designated a light-pollution-free astronomical observation point.

A statue erected in honor of the toadish nickname given to Jersey residents by the French.

An 800-year-old island castle in Guernsey's main harbor.

This 1,300 year old monastery built atop a single rock was once only accessible depending on the whims of the tide.

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

The castle still holds traces of the abandoned Roman fort it was built atop.

One of the few surviving street funiculars in the world.

Recently restored menagerie of Victorian-era beasts.

A giant pineapple, a symbol of hospitality, and an amazing vacation rental option.