The fountain marks the area where hundreds of accused witches were burned at the stake.

A stone arch leads to a cavernous 1930s spring house tucked away in the Pennsylvania woods.

This 700-year-old street food market features baby octopus and soy donuts.

A secret hatch containing two parchments was discovered in this statue over 40 years after its installation.

A walk-in working camera obscura produces 360-degree live images of the San Francisco coast.

The beautiful tunnel that ran from the lobby to Penn Station is still hidden underneath 34th Street.

The world's tallest bridge is also possibly the most elegant.

This frozen tunnel in central Alaska is both an engineering feat and a valuable climate classroom.

Former hunting lodge of a duke who was an avid collector of impressionist works.

Beggars were miraculously "cured" of their fake ailments when they returned home to this 17th century Paris slum each night.

Dedicated to the history and culture of smoking, this small museum now includes a vape lounge.

The spiral staircase hidden inside this giant Parisian column was likely built for Catherine de Medici's astrologer.

An all-American grocery store in Paris sells U.S. "cuisine" like Pop-Tarts and Heinz ketchup to homesick ex-pats.

Noirish green neon marks the location of one of the oldest private detective agencies in France.

This off-limits room in the National Library of France is home to a system of pneumatic tubes, once used to bring books to readers.

In the best of all possible worlds, everyone will get a chance to see this statue in which Voltaire's heart is interred.

A museum which takes visitors to the côté obscure of Paris.

This statue was given to France by the United States to commemorate the centennial of the French Revolution.

With a history of slaughter, feast, and famine, remnants of the pork industry decorate this area--even its church.

A popular shrine where the Blessed Virgin allegedly appeared in 1830, displaying a holy armchair and two incorruptible remains of Lady Saints.

An overlooked marble is the only surviving in-place 18th century example of the measurement that changed how we define distance.

This museum houses an imposing skeleton army comprised of creatures great and small.

A scandalous Art Nouveau collaboration that set Paris all atwitter at the turn of the century.

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