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."

An architectural oddity hides in plain sight on this iconic London bridge.

You will not be able to miss this building.

A statue of the legendary Celtic warrior queen who fought the Roman invaders stands in one of the cities she once destroyed.

Six ravens are kept captive (but well-fed) at the Tower of London to prevent the fall of the Crown.

After nearly 60 years, there's still a bear at Paddington Station looking for help.

Scattered throughout London are ancient remnants of the city's former bounding wall.

The anatomical-pathological collection of a man who changed surgery.

One part local history, 99 parts gruesome haunted house.

Kings Cross Station pays tribute to its role in Britain's best-selling book series.

One of the world's largest collections of pharmaceutical artifacts.

This small museum displays a collection of outsider art and scale models of past "treatments" for mental illness.

One of a series of no-purpose kinetic artworks by Swiss sculptor Jean Tinguely.

This simple apartment may have inspired some of the most important theories in the history of science.

This historic covered bridge contains a series of macabre paintings that communicate one thing: everyone dies.

The alpine falls where Sherlock Holmes apparently met his demise can actually be visited.

This is not only one of the oldest collections in Europe, but also possibly the most beautiful.

This memorial commemorating fallen Swiss Guards of the French Revolution has been called the saddest stone in the world.

The bizarre visions of H.R. Giger, tucked away in a Swiss medieval city.

The only royal palace on U.S. soil has been a territorial capitol, a military headquarters, and a prison for a queen.

This museum of Hawaiian and Polynesian culture is the legacy of the last descendant of the Kamehameha Dynasty.

A particularly creepy abandoned hospital that sparks interest for lovers of the supernatural.

Ant sculptures march up the side of what used to be an iconic spot in punk rock lore.