Around 100,000 bodies are buried below the medieval headstones, many of which mark graves with multiple bodies stacked up to 12 deep.

The topiary maze at the Habsburg hunting lodge.

Two stone columns flank the grand Venice square, but there were supposed to be three.

Venice's "Island of the Mad."

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

A grotesque collection of wax limbs depicting the symptoms of venereal disease.

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

The railway carts travelers to central Athens's highest peak, which offers stunning vistas of the city.

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

This churchyard arbor is surrounded by hundreds of gravestones placed there by author Thomas Hardy.

London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.

Architectural monsters are devouring this palace's every door and window.

One man's stunning attempt at eco-friendly living.

An ancient monastery, a locked room, and a mysterious book heist.

This ancient ruined monastery has been destroyed by fire so many times that it seems like God hates it.

This Rococo church is known as the most beautiful village church in the world, and does not disappoint.

A small but immensely extravagant palace built by the "Night King."

A treasure trove of Renaissance-era funerary art in a Roman church built on top of Nero's grave.

This historic recreationist school churns out warriors that may very well have had a fighting chance in Rome's pits of the day.

A collection of objects supposedly singed by the hands of souls in purgatory.

The skull of the patron saint of lovers lies in the Basilica di Santa Maria in Cosmedin—maybe.

At the crypt of St. Mary of Eulogies and the Dead you are left alone to ponder mortality among piles of skulls.

Rome's semi-secret peephole vista is also a former Crusader stronghold.

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