This London plaque marks the spot where David Bowie's famous alien made his debut.

An artistic tribute to the famous singer, just around the corner from where he was born.

The television series' iconic giant foot was borrowed from this classical painting.

A 2000-year-old Roman amphitheater lies just below Guildhall Yard.

The Pope’s secret escape route.

The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.

The underground sanctuary of a mysterious ancient cult.

Rome's semi-secret peephole vista is also a former Crusader stronghold.

The social hall of this former factory is a Communist-era time capsule.

This mural painted by Keith Haring was done without payment as a gift to entertain the children at the Hôpital Necker.

A beautiful Victorian statue shows France's enduring love of the rhinoceros.

This structure atop a craggy cliff in one of the most beautiful parks in Paris boasts an unbeatable view.

135 bronze medallions mark a French meridian line which once rivaled the hotshot Greenwich timeline.

This museum in a Paris apartment gives a unique look at the iconic French singer's life.

An off-the-beaten-path boutique stuffed with an eclectic collection of upcycled goods.

Where the high court feasted, frolicked, and high courtesans put their royal lovers' diamonds to the test.

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

Medieval museum built over Roman baths that features famous tapestries of a lady and a unicorn.

A mechanized clock where a man fights off a dragon, crab, and rooster.

A scandalous Art Nouveau collaboration that set Paris all atwitter at the turn of the century.

One of Europe's largest supercomputers is housed inside of a disused chapel.

Preserved portions of Athens's ancient defenses are on display in a subterranean parking garage.

This beautiful natural train tunnel is said to grant the wishes of visiting lovebirds.

God's Saharan sandbox of wrath.