The first tunnel to be dug beneath a river, repurposed as an art and museum space.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

A much-maligned monument to teetotalism.

This silent sentry in the crypt below a large Gothic cathedral is often knee-deep in water.

The last moments of the ill-fated Pompeiians, frozen forever in plaster.

This tipsy office building in downtown Prague was originally called “Fred and Ginger.”

This elaborate towering structure was once famed for its revolutionary height.

A medieval replica of King Arthur's legendary table, the Round Table hanging in Winchester Castle was decorated by Henry VIII.

A collection of comics, graphic novels, animation and caricatures devoted to exploring this often overlooked art form.

A treasure trove of astronomical, mathematical, and scientific instruments at Cambridge University.

A turn of the century building boasting some of the most beautiful art nouveau architecture in Prague.

Home to items never before seen by the public.

Several plaster noses are hidden in plain sight around London's Soho neighborhood.

A diminutive memorial marks the site of a successful assassination by a right-wing death squad in America's capital.

Fake rail crossings mark the site of an influential doctor's demise.

An old whaling station now serves to give the public a look at the commercial whaling industry, no longer a part of Monterey's economy.

The stately birthplace of California's statehood.

The oldest U.S. Government building in California, and it's State Historic Landmark #1.

Art Deco and “Wrenaissance” mash-up, this recently restored royal residence has been home to kings and comes with secret monkey passages included.

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

An original apothecary from 1792.

A former major munitions plant that has been converted into a sprawling art space.

This stately building in Alexandria, Virginia was built by Freemasons to honor one of their most famous members.

The privately owned cemetery that holds room for Washington's finest when they step down from life.