The birthplace of the ferocious William the Conqueror, this castle is awash in medieval history.

The tomb of history's greatest potato promoter is surrounded by tubers.

Personal garden filled with mosaics made of recycled garbage.

This Parisian gem is one of the most incredible ethnographic museums in the world.

An underground city of ancient quarry tunnels hid thousands of Allied soldiers in WWI.

The opulent home that inspired Tintin's Marlinspike Hall and the adventures within.

Series of underground houses inhabited continuously for centuries.

This narrow path was cut right into a French mountainside to feed the country's early naval expansion.

This submersible road connecting a French island to the mainland is lined with safety towers for when the tide strands travelers.

Bits of architecture from a town destroyed in World War I now decorate this hotel garden.

The Church of the Annunciation was carved into the face of a cliff, just like the rest of the town of Haute-Isle.

Since ancient times these picturesque springs have been providing bathers with healing waters.

A tiled, multi-level garden of survival in Lyon.

A French valley with forests so lush it was nicknamed "the Small Amazonia of the Pyrenees."

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

Museum in a swimming pool where the water still flows.

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

An iconic and eccentric bar for "Manouche" Jazz music keeps expanding its space—and its influence.

Lyon, France is home to two remarkably preserved Roman theaters, one dating back to 15 BCE.

This little-known relic crypt holds stolen parts of a Roman Empress.

Sleep in a climate-controlled plastic bubble for the night.

The floorboard scrawling of a tragic madman is on public display outside a Paris hospital, much to the dismay of its opponents.

Beautiful carved tunnels.

The fantastic architectural models of a French traveler.