One of Australia's largest secondhand bookstores.

Australia's largest medical museum featuring a 19th-century pharmacy.

This gracefully curving formation looks like a massive wave that was suddenly turned to stone.

An ancient rock engraving shows Aboriginals used their advanced knowledge of the stars to hunt and gather.

This extraordinary geological oddity resembles human-made pavement.

Dilapidated ruins that once treated a notorious young serial killer, currently hosting vandals, squatters, and ghost hunters.

A castle hand-built by a Spanish dreamer in the Australian tropical jungle.

A former imperial sea-fortress and Soviet prison.

An empty relic of the Moscow Olympics crumbles away in Estonia's capital.

This medieval Estonian tower provides access to a series of tunnels that have been home to soldiers, punks, and fine art.

"There's nothing there," and other lies the KGB told us.

A once-secret library of Freemason history in Catalonia.

A stately palace has been converted into the world's largest cannabis museum.

Possibly the oldest church in Barcelona, this basilica has its pagan and Christian mythologies all mixed up.

This small chapel is built of human bones and decorated with a golden skeleton.

Legacy of the earthquake that nearly wiped Lisbon off the face of the Earth.

Catering to broken dolls for almost 200 years, this repair shop is now a charnel house of doll parts.

A Nesting Doll of Churches.

A mysterious chasm in the heart of the ancient Roman Forum, the Lacus Curtius was once believed to be a gateway to hell.

One of several skulls claiming to belong to the beheaded St. John the Baptist is on display at this Roman church.

This former Roman Catholic Church still contains the embalmed hearts and organs of 22 popes.

An alchemist's "magic door" stands in the middle of a Roman park.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

Installed in an act of one-upsmanship, the annual sundial in this church is also a symbolic victory for the Gregorian calendar.