This Hungarian castle was built out of cardboard and wood until it proved so popular that it got upgraded to stone.

A random tree outside a Budapest hotel has become a DIY shrine to the late singer.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

Budapest's Communist-era statues, banished to the suburbs.

Thousands of rusting train cars have been slowly falling apart on the edge of Greece's second largest city.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

Ancient Greek oracle of the dead.

Monasteries on rock pillars, once accessible only by frayed ropes.

The remains of 40,000 humans, meticulously stacked in a tiny churchyard shed.

The remains of a town so thoroughly destroyed by French forces that the citizens simply left.

An Italian crevasse filled with abandoned buildings gives visitors a look at the world without humans.

Abandoned cemetery of the former Psychiatric Hospital of Volterra.

Natural cathedral designed by Italian artist Giuliano Mauri.

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

A small island less than half a mile from Venice is a forbidden island with a dark and twisted past.

The oldest of Venice's plague quarantine stations, designed to keep the medieval city safe from disease.

This Venice bookstore has resigned itself to constant flooding by keeping its books in bathtubs and boats.

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

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

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

Largest necropolis in the Mediterranean.

Hauntingly beautiful totem poles left by the Haida.

This Tang Dynasty behemoth is the biggest Buddha in the world.

Three bridges and one giant canyon make up this fantastic Spanish settlement.