For more than a century, revolutionary graffiti has marked the wall of a Parisian church.

Known as the "Dodo Manège," this carousel features a herd of animals that have disappeared—or may be gone soon.

Rodin's famous depiction of Dante's 'Inferno', amidst a sculpture garden of many of his other works.

Sofia's legislative center is continuously reinventing itself.

A striking symbol of the Bulgarian capital.

A vast Communist-era exhibition space in the Bulgarian capital.

A Bulgarian monument to Russia's role in World War II is constantly being painted in pop culture protest.

"Holy Wisdom" overlooks the city that became its namesake.

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

This charming cobbled backstreet is the most Instagramable street in Paris, much to the residents' annoyance.

Abandoned railway line circling the city of Paris.

A model train wonderland hidden beneath Gare de l'Est station.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

An artsy hidden staircase leads to breathtaking views of San Francisco.

A huge musical instrument played by the ocean.

The industrial architecture honors the laborers who brought the Exposition Universelle of 1900 to life.

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

This triumphal arch celebrating the Sun King's conquest of Lille is a masterpiece of military architecture.

Tables of secondhand books fill the inner courtyard of this 17th-century stock exchange.

This banal Parisian entranceway is not what it seems.

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.

A counter-culture bookstore like no other hides in plain sight in the streets of Paris.

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

Ghosts of France's colonial past.