This Polish cave has housed a dragon, a brothel, and an enduring legend.

Launched by Napoleon's soldiers more than 200 years ago, a cannonball remains embedded in the tower wall.

Handsomely crafted representations of our round planet.

A spherical "micro-nation" in the heart of Vienna.

The crypt of the imposing Stephensdom holds royal intestines and thousands of skeletons.

A tropical paradise just a short trip from the opera house is filled with beautiful winged creatures.

The final resting place for the remains of 143 Habsburg royalty.

The beautiful baroque library of the Hapsburg empire.

The only Roman honorific column in Istanbul.

Wash down heaping platters of meze with raki at one of the city's best taverns.

Climb a steep hill in 90 seconds on the second-oldest urban subway in the world.

This crucial gathering spot along the "hippie trail" still displays old notes between traveling beatniks and backpackers.

A gorgeous, Gaudí-esque stairway constructed in the city of Istanbul by a prominent Jewish family.

1513 Turkish world map, full of European state secrets and snarky commentary.

Legend says if you stick your thumb in the hole and it gets wet, your wish will be granted.

A small etching on the white marble parapet was written in runic script by a Viking mercenary.

The ornate miniature mansions were built for Istanbul's feathered residents.

Five sultans and their families rest in eternal splendor, teeming with overlooked beauty and drama.

A marvel of Byzantine engineering under the streets of Istanbul.

Does this 10-foot-tall statue carved into a rock face depict a king afflicted by a skin condition or a Buddhist figure?

Thousands of slain Soviet soldiers are buried within the shadow of this enormous obelisk.

The largest fountain in Bratislava.

This spaceship sculpture in the middle of the Slovakian capital looks like it just crash-landed.

This Slovakian statue of an emerging sewer worker might just be a bronze peeping tom.