A 16th-century fountain marks the site of a lost medieval cemetery once filled with mass graves.

Remains of Roman amphitheater hidden in a sleepy quarter of Paris.

This life-size replica of the Statue of Liberty's flame is also a tribute to Princess Diana by default.

The water-powered carriages are long gone, but for over a century this funicular railway has been the fastest route to the highest point in Paris.

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

The first green space constructed on an elevated viaduct.

This Parisian fountain is a little bit fantasy and a little bit nightclub.

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

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

A Parisian cemetery where the elite and artistic are interred beneath an eccentric collection of tombs.

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

Paris' linguistic guide to the international language of, yes, love.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

Notorious artist squat renovated into legal studios.

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

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

This nearly 200-year-old restaurant's history includes an exiled French prince, JFK, and a very hungry Daniel Webster.

Millions of numbers carved in glass represent the tattoos forced upon victims.

A centuries-old church stands as a testament to Boston's "father of architecture."

Dedicated to one of the darkest moments in Irish history, this memorial has faced its fair share of backlash.

What was once a true peninsula has now been filled in, causing the water to recede and leaving many streetside "waterfronts" and landlocked "islands."

This impressive Boston holy house is the American mecca for Christian scientists.

A former waterfront market is now in the center of town due to some interesting Boston engineering.

The site where Charles Dickens gave his first public reading of "A Christmas Carol" in the US.