This grisly effigy displays an early Christian martyr who was skinned alive and beheaded.

Da Vinci's equestrian statue, 500 years in the making.

The mark of the Devil's horns on a marble column in Milan.

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

This curious building hides eclectic details like medieval gargoyles alongside naked angels and Art Nouveau mosaics.

Small on the outside, big on the inside, this church is an astonishing act of visual deception.

The secret medieval communication system will whisk your words above the noise of the crowd.

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

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

This small 16th-century church in Athens is almost entirely surrounded by a modern building.

This gem is often wrongly overshadowed by the larger, newer Metropolis church in Athens.

150 or so scrounged-up lamps, chandeliers, and lanterns light up this alley in central Athens.

The ruins of an ancient Roman tomb hidden in the basement of a trendy clothing store.

A tiny Greek Orthodox church from the Ottoman era hides on a busy city street.

There are many Byzantine-era churches still standing in Athens, but this is the only one with a 2,500-year-old column rising through its roof.

According to legend, this ancient column contains healing properties.

This mystical orb covered in strange symbols is thought to have been used in ancient Greek magical rituals.

The only surviving choragic monument is a trophy awarded in 334 BC for the winning dramatic chorus.

At this ancient settlement at the foot of Mount Babadağ, honeycomb tombs are carved into a round cliff.

A computer bug so primitive it was an actual insect.

A museum dedicated to the Spanish occult in a town that was terrorized by the Inquisition.

This awesome Spanish castle is so fantastical it was actually used on Game of Thrones.

Ming Dynasty necropolis raided during the Cultural Revolution.

The oldest church in Mantua was buried for centuries under the facades of other structures.