Secret refuge and museum of the Duke of Florence.

This private skyway is filled with art and was expanded explicitly so that Hitler could appreciate a river.

A slightly creepy gallery of plaster cast models in the same museum as Michelangelo's David.

Diego Rivera hid various people and symbols in his first large-scale mural project.

Once at the center of U.S. finance, the historic Trading Room was meticulously recreated piece by piece and rebuilt in the Art Institute.

Illegal drag racing two stories beneath Chicago’s streets.

To find the "unicorns of the deep" you've got to go downstairs.

The twin towers in this Chicago fountain use 50 foot tall video screens to spit on people.

This historic hotel invented the chocolate brownie.

An enormous park-like oasis, full of famous Chicagoans' graves.

Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.

Many of Edinburgh's more unsavory characters spent their final days behind this door while awaiting their executions.

This early version of the guillotine was used to execute the man responsible for its construction.

This Roman relic was discovered in Scotland by a mudlarking ferryman.

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

There are plenty of wonderful panoramic vistas in Edinburgh, but not many are hidden smack in the middle of the Old Town.

The taxidermy remains of the first mammal ever cloned from an adult cell are on display in Edinburgh.

The dance of this huge clock is a magnificent and eerie commentary on good and evil in the history of humankind.

Another entry into the world of Edinburgh's pop-up artworks.

This obscure walkway links Edinburgh’s Old Town with one of the city's prime vantage points.

Neon artworks light up this dark Edinburgh tunnel.

This severely painted building has a twisted connection to the witch hunts of the 1640s.

A remarkable feat of Victorian engineering across the Firth of Forth.

This repurposed church offers a more literal way to get closer to the heavens.