Cat art as far as the eye can see.

An Amsterdam street lined with antique shops each one dedicated to a different obscure collection.

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

In this cobwebbed old operating theater, you can practically hear the screams of the unanesthetized patients.

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.

A kaleidoscopic warehouse-maze of handmade neon signs.

The last Victorian market in Belfast.

This hidden museum examines the complex history of the country's law enforcement.

It was once nicknamed "the most bombed hotel in Europe."

These barriers stand as stark reminders of Northern Ireland's troubled past.

A particularly disconcerting tribute to Irish martyrs.

Though they've since been renamed, these two streets hint at Dublin's darker days.

A nun spent 16 years painting the stunning Celtic mural that covers the interior of this WWI memorial.

The mummified heart of a saint lives on in this church—after a brief hiatus when it was stolen.

The only royal palace on U.S. soil has been a territorial capitol, a military headquarters, and a prison for a queen.

A model of a galactic embassy is hidden in plain sight along the highway, proposed by a UFO religion to find the aliens that created life on Earth.

An ancient Scottish rock formation said to be the gravesite of a giant remains ensconced in legend and intrigue.

The most iconic structure in Scotland has been home to bishops, colonels, and Sean Connery characters.

With well over 130 falls and cascades to brag about, Hamilton, Ontario has earned its stripes as the waterfall capital of the world.

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