This small, ancient Roman temple was once a church dedicated to the patron saint of penitents.

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

This curious, round temple is the oldest still-standing marble building in Rome.

Ancient ruins hidden underneath a modern luxury hotel.

The "Greatest Sewer" of ancient Rome is one of the oldest sewer systems in the world, and is still in use.

The celebrated eyesore created by starry-eyed sweethearts.

One of the last umbrella repair shops in Paris upholds the nostalgic art of umbrella making.

This lesser-known Frank Gehry building houses a treasure trove of cinema history.

Claude Monet was baptized in this lavishly ornate Paris church.

The Argonaute submarine was the French navy's pride and joy in the 1950's.

The tradition of open-air secondhand and antiquarian bookselling in Paris dates back to the Renaissance.

This bridge was constructed from the rubble of the infamous Bastille.

Got apples?

A series of abstract, silly sculptures represent the works of a great modern classical composer.

The narrowest street in 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.

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

19th century pendulum and a clock restored by a rogue group of guerilla artists.

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

France's national museum of scientific and industrial instruments.

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

High atop the Eiffel Tower is a small apartment built exclusively to entertain the science elite and make the rest of Paris jealous.

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