The construction of a tram line unveiled hidden remnants of the old medieval city.

One of the world's most complex timepieces.

An enchanting work of outsider art, full of whimsical sculptures and carvings.

A unique underground structure dating back to the 1st century BC.

Ivy-covered Medieval tunnels cut through this charming town in France's Loire Valley.

The remains of 40,000 humans, meticulously stacked in a tiny churchyard shed.

The 16th-century church was kept in its ruined state as a reminder of the casualties of World War I.

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

A medieval church with largest and oldest collection of Renaissance frescoes in France.

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

There has been an astronomical clock on this spot since the 14th century.

This collection of French root art looks like an indoor fairy wonderland.

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

A chapel on a volcanic core, marking the end of a successful journey.

Hundreds of secret cabinets built into the walls of legendary poisoner's private work room.

This French castle is said to have once held the Holy Grail but is now a gorgeous mountaintop ruin.

The world's largest reflecting pool is just two centimeters deep.

A mosaic-tiled house built by graveyard sweeper Raymond Isidore.

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

A medieval military street hidden beneath a charming French fishing village.

Beautiful carved tunnels.

A well-preserved medieval village nested on a rocky outcrop and surrounded by a network of cliffs, natural bridges and canyons.

This stunning natural double arch, the largest in the Alps, went undiscovered until 2005.

Two small chapels housed inside an ancient tree.