A rocky sea serpent hides caves, blowholes, and a spectacular natural bridge.

An impromptu shrine appeared shortly after beloved "Torchwood" character Ianto Jones was killed off the show.

Bullet holes in the church wall are a reminder of the violence that followed the assassination of a high-ranking Nazi officer.

This tipsy office building in downtown Prague was originally called “Fred and Ginger.”

An extraordinary mechanical calculator designed by the mathematician and philosopher Gottfried Leibniz.

The quiet field that inspired one of the most famous songs of all time.

A labyrinthine underworld of tunnels and caverns hides beneath the city.

Hidden in a grotto 26 feet below Nottingham's oldest hotel, this stylish subterranean drinking den is notoriously hard to find.

In the early Roman Empire, people deemed traitors and criminals were tossed to their deaths from this rock.

Brass cobblestones mark the places where individual Holocaust victims were taken from their homes.

The spot where the fascist dictator made some of his most famous speeches including declaring war on Britain and France.

A mysterious chasm in the heart of the ancient Roman Forum, the Lacus Curtius was once believed to be a gateway to hell.

One of the most important yet well-hidden museums dedicated to the history of medicine.

Inside this McDonald's you can dine on your Big Mac and fries next to a 2,500-year-old Roman wall.

This ritzy Italian market is built around a statue of an unforgiven heretic who was burned for his belief in an endless universe.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

The train platform where Jews were sent to concentration camps is now preserved as a Holocaust memorial.

The odd depiction of the Virgin Mary and baby Jesus is rooted in the Catholic Church's eradication of Catharism.

This giant middle finger statue sends an unambiguous message to Italy's bankers.

A Milanese café entirely designed by the American director Wes Anderson.

An ossuary built in 1210 to collect bones from the Ospedale Maggiore of Milan.

Hamburgers are intensely proud of their tunnel beneath the river.

A beloved Chicago music venue offering cold beer and lots of “Friendly."