These hut foundations are believed to be the residence of Romulus, founder of Rome.

A deep mark on the remains of a Roman temple, believed to be left by a legendary warrior.

This ancient Roman arch misled treasure hunters for centuries.

The ruins of an abbey believed to have been founded by Charlemagne in the 9th century.

The mystic whose incorrupt corpse still attracts the faithful.

A treasure trove of Renaissance-era funerary art in a Roman church built on top of Nero's grave.

This ritzy Italian market is built around a statue of an unforgiven heretic who was burned for his belief in an endless universe.

The underground sanctuary of a mysterious ancient cult.

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

A cluttered and astounding collection of antiquities and curiosities.

This wildly-tiled artist's palace is a living and growing account of the creator's life, loves, and labors.

An incarceration museum on the spot of possibly the oldest prison in England.

Hidden beneath the streets of London is a secret subway that only carried mail.

This South London cemetery holds the remains of more than 15,000 people.

This collection of illusory paraphernalia has been culled from the history of London's premier magician's club.

Kings Cross Station pays tribute to its role in Britain's best-selling book series.

An airy Art Deco space devoted to the weird and wonderful folk art traditions of Mexico.

This enormous abandoned factory is now a makeshift graffiti gallery.

Street artists transformed this abandoned industrial neighborhood into one of Europe's largest graffiti exhibitions.

Some of the greatest minds in the history of Hungarian art and science converged in this café.

A museum dedicated to a secret military hospital hidden beneath a castle in Budapest.

The mummified right fist of a 1,000-year-old saint-king sits inside an ornate golden reliquary.

The romantic garden was the epicenter of the Hungarian art scene in the 1880s.

From Austrians to Nazis to Soviets, this historic Budapest fortress has a history as complex as the city itself.