Where the high court feasted, frolicked, and high courtesans put their royal lovers' diamonds to the test.

France's national museum of scientific and industrial instruments.

This 1,300 year old monastery built atop a single rock was once only accessible depending on the whims of the tide.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

Bring your own cardboard to the slippery slopes of concrete hidden in a neighborhood park.

Staircase winds down the side of Telegraph Hill through gardens, wild parrots flying overhead.

A library built during San Francisco's pioneer times is a student's retreat, bibliophile's sanctuary, and chess player's delight.

An artsy hidden staircase leads to breathtaking views of San Francisco.

A huge musical instrument played by the ocean.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.