Cave on extinct volcano, once home to famous mathematician Pythagoras.

Hideout of thieves, monks, and goat-footed gods.

Giant marble phalluses on the sacred island of antiquity.

This legendary city has been a tourist attraction for centuries.

Monasteries on rock pillars, once accessible only by frayed ropes.

Louise Bourgeois' 30-foot-tall steel spider sculpture.

Near the former site of numerous witch burnings, this lavish Edinburgh mainstay pays homage to Scotland's brutal history.

Once home to a Scottish baronet, this 18th-century historic house doubles as a legendary art space.

This 16th-century house tells the city's history through old artifacts and quirky tales.

This charming old building's loose connection with the Scottish Reformer is what saved it from demolition after it split apart.

Small museum dedicated to the founder of electromagnetic theory.

This dramatic landscape hidden on the Isle of Skye looks as though you've stepped into the magical realm.

The largest permanent Monopoly board makes one of the longest games even bigger.

Home to 10,000 medical specimens including the remains of Rudolf Virchow's extensive collection of pathological specimens.

A narrow passage next to a cafe leads to a courtyard exploding with murals, tags, and paste-ups.

A closed London rail station created to cart away the dead still bears the marks of attempts to make it less morbid.

After nearly 60 years, there's still a bear at Paddington Station looking for help.

Rebuilt remains of a temple to Roman god Mithras.

This hidden stream beneath Indianapolis makes an appearance in the best-selling novel "Underground Airlines."

A wacky two-story folk-art assemblage of carved and found objects, with lights, motion, and sound now in need of financial support.