A morbid secret lies hidden within the beautiful walls of the Boston Athenaeum.

One of the oldest used bookstores in the U.S. has been selling antiquarian treasures since 1825.

The oldest Italian café in Boston, this spot also serves as a veritable museum of vintage coffee ephemera.

Two thousand artifacts from around the world collected by one woman who loved to travel.

A beautiful Victorian-era cemetery, complete with a miniature village.

This Boston medical museum features the skull of the famous medical case of Phineas Gage.

An enormous, inside-out glass globe built in 1935.

The spectacular history of spectacles on display.

Debatably clever, or just plain honest hotel advertised as "The Worst Hotel in the World."

In the days before house numbers, these colorful signs held clues about various buildings' purposes.

A nomadic museum known for its art exhibitions about religion and faith.

The former home of a mad diplomat is said to still be marked in bloody, arcane scrawls.

The attic of a four-century-old canal house hides a clandestine church.

A Dutch passageway's artistic, aquatic-themed makeover pays tribute to the capital city's famed waterways.

This historic Amsterdam bar used to accept sailor's monkeys as payment.

The world's first zoo for microbes collecting the horrible and wonderful things living on and around us.

Established in 1638 to battle the Black Death, this botanical garden is a treasure trove of rare flora.

Cat art as far as the eye can see.

A curious collection dedicated to human and animal anatomy and pathology.

Museum preserving torture methods from the past.

A floating cat sanctuary on an Amsterdam canal.

An Amsterdam street lined with antique shops each one dedicated to a different obscure collection.

The world's only museum devoted to the wonders of fluorescence.

Op-art architecture designed for happiness.