Visit the ancient, mysterious Roman catacombs ... in the Netherlands.

A rare tour of an aristocrat's private home reveals valuable 17th-century paintings from artists like Rembrandt.

This museum housed in a former brothel explores the past and present of sex work in Amsterdam.

A Portuguese Jewish cemetery filled with stunning grave monuments that date back to 1614.

The palace window through which Protestant nobles flung two Catholic regents, thus sparking the Thirty Years' War.

Synagogue built from the stones of Solomon's temple contains the golem of Prague.

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

Walk through Czech history in Prague's largest graveyard.

The hidden lair of an alchemist rediscovered in a 2002 flood.

Two stunning 17th-century libraries and a cabinet of curiosities.

A medieval weapon rumored to have been used by the brilliant poet himself.

Renaissance hospital featuring a rotating door into which unwanted babies were dropped.

The bomb-ravaged remains of of a colossal Neptune.

This tiny chapel withstood a massive mudslide and flash flood.

This amazing medieval fortress stands atop a promontory along the famous Cinque Terre.

A lover's walk between hilltop towns, decorated with graffiti love notes.

Five candy-colored villages on the Italian Riviera.

This unassuming bookstore in the heart of Madrid is one of the oldest in Spain.

Order cookies baked by cloistered nuns in a 400-year-old monastery.

The morbid items in this small and hidden museum are not for the weak stomached.

A lush indoor jungle fills this bustling Madrid transportation hub.

An ancient Egyptian temple in the middle of Madrid, Spain.

Madrid's romantically ornate crystal palace has been offering shelter to plants and art for over a century.

The oldest restaurant in the world is this old-world Spanish eatery, still known for its suckling pig.