A series of caves under Castle Hill that once held the prisoner Vlad Tepes, better known as Count Dracula.

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

The geographical center of Budapest is marked with a 10-foot-tall stylized zero.

Central Europe's largest collection of mini-bottles is on display at this museum devoted to a bitter Hungarian liquor.

Legions of Roman soldiers bathed in this ancient spa complex under a Budapest transit station.

A Trabant car, a kangaroo statue, and a plethora of plants take over this abandoned-factory-turned-bar.

A forgotten graveyard lost in the tangles of an overgrown garden.

Possibly the world's largest hourglass only needs to be reset every New Year's Eve.

Sitting beneath an unremarkable residential building is a museum devoted to classic Pinball.

This shining multicolored metro station deep under Naples is said to be the most beautiful in Europe.

A factory director designed what was the world's longest suspension footbridge in 1923 so his employees could get to work safely.

Crossing this suspension bridge feels like walking through the sky, a fitting tribute to the head of the Apollo program.

This beautiful park on the outskirts of Rome protects the ruins of two colossal ancient aqueducts.

This abandoned Brutalist treehouse is a hidden architectural relic.

One of the largest caves in the world open to the public.

A labyrinth of ancient tunnels hidden below the city holds the ruins of 2,500 years of history.

This quaint Italian town keeps losing ground as the sides of its plateau slowly erode.

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

An Italian hillside ghost town.

This 16th-century monastery has been turned into a surrealist architecture compound.

Sitting on an Italian hilltop is this surreal fortress built by the mad inventor of electrohomeopathy.

The last moments of the ill-fated Pompeiians, frozen forever in plaster.

Hidden in an Italian forest is a completely homemade amusement park that has taken a lifetime to create.

2300-year-old Roman road connecting the empire.