Why a column on the entrance is inscribed with a verse from the Quran is one of Sicily's many mysteries.

This skeletal, unfinished Gothic church once housed a miraculous masterpiece by Raphael.

This triumphal 16th-century arched gateway leads to the oldest street in Palermo.

This Arabesque Italian castle was built with a primitive, if ingenious, air-conditioning system.

Haunting graffiti left by prisoners of the Spanish Inquisition.

Every inch of this chapel is covered in craftsmanship from across the world.

Behind medieval walls in a corner of bustling Palermo is a breathtaking former mosque once inhabited by a wolf-taming hermit.

Cave shrine on Monte Pellegrino.

This mosaic-lined medieval church was built by the world's first admiral and still holds mass in ancient Greek.

Thousands of well-dressed mummies below a monastery.

His "Lionheart" is entombed separately from the rest of his body.

The narrowest street in Paris.

This medieval tower is all that remains of the castle where Joan of Arc was held before being burned at the stake.

One of the largest ochre quarries in the world, hidden in a limestone landscape.

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

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

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

Massive puppet-automaton machines created by French artist collective Machines de l’Ile.

The former home of France's controversial pop maestro is almost completely covered in ever-changing tributes and graffiti.

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.

Natural history museum celebrating biodiversity with a parade of taxidermy animals.

Twelve grave-faced marble angels guard the emperor's tomb at Les Invalides.

The ruins of a Duke's bucolic dream, where camels once roamed alongside "Dutch" windmills and faux-Italian vineyards.

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