The hidden "ballroom" under a mansion lake was built by a criminal who ate a cyanide pill during his trial.

The world's first purpose-built motor racetrack was destroyed by the outbreak of two world wars.

Cryptic messages embedded in the New York City sidewalk.

Amidst the bustling streets of Dublin, there is a hushed garden that is dedicated to "All those who gave their lives in the cause of Irish Freedom."

The gorgeous library at Trinity College is home to remarkable treasures of Irish identity.

A labyrinthine network of chambers with a storied past hides below Edinburgh's South Bridge.

A verdant 17th-century-style garden hidden along Edinburgh’s Royal Mile.

Overlooking the burial ground is a tower designed to prevent thieves from snatching the recently deceased.

One of the oldest scientific gardens in Britain, containing more than 13,302 plant species in its core collection.

Protecting the dead from opportunistic body snatchers.

A book bound in the skin of an infamous criminal, along with countless other specimens.

Tiny effigies of the victims of Edinburgh's famous Anatomy Murders.

A 18th century graveyard and its astonishing cortege of macabre iconography.

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

This early version of the guillotine was used to execute the man responsible for its construction.

The taxidermy remains of the first mammal ever cloned from an adult cell are on display in Edinburgh.

The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.

Several plaster noses are hidden in plain sight around London's Soho neighborhood.

A 1,215-foot tunnel transports pedestrians beneath the River Thames.

A historic arboretum and non-conformist, non-denominational park cemetery.

This South London cemetery holds the remains of more than 15,000 people.

At Monet's beloved home you can still see the Japanese bridge, waterlilies, and weeping willows that were the subjects of some of his most iconic paintings.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

France's most famous cemetery, with some of its most curious tombs.