This off-limits room in the National Library of France is home to a system of pneumatic tubes, once used to bring books to readers.

The famous winding walk at Chartres is surrounded in mystery and myth.

A Gothic cathedral created from volcanic rocks.

The largest underground church in Europe.

This salt marsh in Southern France is as pink as the flamingos that inhabit it.

This natural French spring has been turned into a magical grotto by Roman and medieval constructions.

The subterranean "lake" below the Paris opera house inspired the Phantom of the Opera's lair.

A subterranean shelter remains intact under a busy Paris railway station.

This Parisian café sticks almost exclusively to an ethos of reuse.

Egyptian Revival movie palace abandoned for decades and restored in 2013.

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

The very center of Paris is surrounded by a bevy of strange good luck rituals.