Edinburgh’s version of the Sistine Chapel is this former church, with an interior covered in paintings done by one woman over the course of nearly a decade.

The best preserved Paleochristian basilica in Rome hides a number of oddities and secrets.

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

More sculpture than building, this architecturally significant temple was built on the spot of Saint Peter's crucifixion.

One of seven Jewish catacombs in Rome and one of only two open to the public.

Installed in an act of one-upsmanship, the annual sundial in this church is also a symbolic victory for the Gregorian calendar.

The Pope’s secret escape route.

One of several skulls claiming to belong to the beheaded St. John the Baptist is on display at this Roman church.

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

Jesus' footprints and the first catacombs in the world.

The underground sanctuary of a mysterious ancient cult.

The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.

An alchemist's "magic door" stands in the middle of a Roman park.

Architectureal fantasy quarter of Rome.

This hidden Art Nouveau courtyard is an opulent feast for the eyes.

Nestled in the heart of Milan is a real wunderkammer of morbid curiosities.

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

Artistic tombs, monuments, and a beautiful "Hall of Fame" lurk inside this cemetery.

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

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

Just across from the "Last Supper" painting is the famous painter's vineyard, a gift received for creating the masterpiece.

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

Milan's duomo is covered in beautiful carving including a curious "dinosaur-like" beast.

Long-abandoned art nouveau baths beneath Milan's Piazza Oberdan.