Down a cobblestone alleyway is a museum dedicated to Romanticism, with a secret garden.

The history of radiation is on safe display at the foot of a radiation science laboratory.

A grotto-like lodge decorated with gilded mosaics, rocks and a noisy waterfall was the setting for the most sumptuous pleasure house of 1900s Europe.

Medieval museum built over Roman baths that features famous tapestries of a lady and a unicorn.

Inside a former cabaret, seven floors of erotic art.

Behind the pink curtain, Au Bonheur du Jour, an art gallery of erotic archives.

A museum of carnival attractions where you are invited to ride the rides.

One of the oldest medical collections in Europe focusing on rare surgical instruments.

The macabre collection of Jacques Sirgent, an expert scholar on the undead and all of their trappings.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

Despite being considered a thoroughly American sport, basketball's oldest surviving playing field is found in the basement of a Paris YMCA.

The personal library of the founder of modern neurology is open to visitors.

Open air sculptures by an eccentric and loin-clothed hermit.

The streets of a sleepy Spanish town proudly exhibit some of the world's finest graffiti.

Giant topiary dog once played a role in a terrorist bomb plot.

An accidental trick of light casts the perfect shadow of a pilgrim of the Camino de Santiago against the cathedral wall.

Lava stone structures possibly dating back to the 19th century may have been a stopping point for voyagers between ancient Egypt and the Mayan Civilization.

According to the Guanches, the aboriginal people of the Canary Islands, the king of evil lives inside this volcano.

This "flat geyser" bubbles up out of the ground periodically like a disappearing river.

12th-century holy complex shares land with a natural park full of heavenly waterfalls and raptors.

The remains of an encyclopedic sculpture garden later used as an internment camp.

This quaint Spanish village agreed to be painted blue as a marketing stunt but found that they preferred it that way.

Thanks to an acoustic anomaly, this unassuming stone bench has heard one hundred years of secrets.

A completely underwater art museum sends a stark message about humans' impact on the environment.