Dating back almost 400 years, the oldest public collection library in the United Kingdom was once the study hall of Karl Marx.

Wedged between two buildings at the Great Ormond Street Hospital is this secret music installation.

Tiny effigies of the victims of Edinburgh's famous Anatomy Murders.

The world's largest collection of witchcraft regalia.

A Victorian natural history and ethnographic museum with wonderful turn-of-the-century, science-book-esque evolution displays.

360° views of the city plus five floors of optical illusions and hands-on science.

A island reachable by a causeway at low tide is possibly one of the earliest Western European locations to be identified in text.

A saintly relic hidden in a Prague church basement.

Tiny communists hammer away on the Olomouc Astronomical Clock.

One of the most beautiful bookstores in the world hides a neo-Gothic interior behind an art nouveau facade.

A genuine Little Shop of Horrors.

The amazing wonder cabinets of a very rich Austrian archbishop.

Hidden away in a modern library are the remains of one of the 18th century's most celebrated wunderkammers.

An island filled with hundreds of hanging, decomposing, decapitated dolls.

Extraordinary sculpture garden created by an eccentric English poet.

One of the world's largest ice festivals dazzles visitors for over a month with radiant sculptures and carvings.

The largest cave shaft in the world is home to thousands of birds and popular with BASE jumpers.

A massive underwater sinkhole made famous by Jacques Cousteau.

Beijing's version of Disneyland, completely abandoned, mostly destroyed.

Jurassic theme park in the small town of Erlian.

Remnants of a Victorian garden feature sitting in public woodland.

An ethereal glowing blue ocean cave in Croatia.

These spooky and unusual stone formations create an underworldly landscape.

The bizarre visions of H.R. Giger, tucked away in a Swiss medieval city.