The crypt of the imposing Stephensdom holds royal intestines and thousands of skeletons.

A small museum filled with over 1,000 clocks, and one particular clock calibrated to run until the year 9999.

The last of Philadelphia's wood-paved streets is now a landmark of terrible engineering.

This Toronto garden collects stares and tchotchkes in equal measure.

A well-preserved network of cavernous tunnels have spent silent centuries removing Toronto's waste.

A book collector's dream, this Toronto bookstore has the world's first "Biblio-Mat," a random book vending machine.

Secret Swing.

One of Canada's most incredible rare book collections holds hundreds of thousands of gorgeous tomes that the general public can touch.

Willy Wonka would love this weird half-a-home.

Lost subway station nestled beneath Toronto's busy commuter line.

Naturally protected city carved from a rock face.

In this historic region, homes and churches are carved into ancient volcanic rock formations.

The deepest underground city in Turkey was designed to protect 20,000 people behind massive stone doors.

Live a night as a Byzantine King, with a minibar and private jacuzzi.

Vast stretch of tide-pools with a unique Moroccan charm.

This unique exhibit "Dialogue in the Dark" reverses roles as the visionless become guides and the sighted become ‘blind.’

The Icelandic Sea Monster Museum explores the area's history of aquatic cryptid sightings.

This collection of unique liquids allows visitors to wander the waters of Iceland's glaciers.

A decommissioned submarine base makes a great space for graffiti art.

Disused seaplane hangar gets a second life as the jaw-dropping home of Estonia's museum of maritime history.

The gutted remains of this Estonian mansion are a monument to a tragic love.

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

A former imperial sea-fortress and Soviet prison.

This abandoned fighter jet launch center is now a haunting street racing course.