Thousands of tourists and residents in Cologne affix "love padlocks" on the Hohenzollernbrücke Bridge to symbolize their affections.

Terrifically morbid cemetary and site of famous Paracelsus' grave.

The old observatory in Copenhagen has a spiral corridor used as a racetrack.

You can spot this teeny tiny stained-glass window from the Bonifacius bridge.

The compass on its front was a handy tool for 17th-century merchants who needed to know the direction of the wind.

This gruesome biblical parade celebrates the one day a year that a bit of Jesus' blood turns to liquid.

Christ's blood allegedly preserved in a Belgian town.

Historic fortifications form the boundary of Vatican City, but it’s not entirely surrounded by walls.

This equestrian statue of Constantine the Great has been the subject of criticism for centuries.

Breathtaking and huge 430 year old maps of Italy.

This small church was constructed over the ruins of three temples dating to the Roman Republic.

An ancient Roman temple first dedicated to an emperor's wife is now a church.

A rather vulgar example of the transition from Latin to the Italian vernacular.

This ancient Roman arch misled treasure hunters for centuries.

A monumental fountain in Rome features a large statue of Moses that has been criticized for centuries.

This one-of-a-kind Roman arch is not actually dedicated to the god Janus.

Remnants of a 4th-century church with vivid medieval frescoes and ancient sarcophagi hide beneath this old basilica.

St. Francesca Romana, patron saint of drivers, resides in the church she founded.

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

This is the oldest Roman-made bridge in the city still existing in its original state.

The mystic whose incorrupt corpse still attracts the faithful.

This hill made entirely of ancient Roman jars was simply a garbage dump to the people of the time.

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

This ancient Roman prison is decorated with an upside-down cross not as blasphemy but as saintly tribute.