A modern-day Lascaux cave underneath Paris.

A lone cannonball remains lodged in the walls of the Hotel de Sens as a sober reminder of a revolution.

The oldest stone house in Paris was built by its most famous alchemist.

Mural made of 100,000 pieces of hand blown glass, and until recently, the largest glass mural in the US.

Philadelphia boasts one of the best — and most often overlooked — traditional Japanese gardens in North America.

A network of concealed passageways lies within a busy London Underground station.

The Metropolitan Police refurbished the blue box (perhaps not coincidentally) the same year "Doctor Who" returned to TV screens.

An small and easily overlooked archaeology museum chock full of Egyptian artifacts.

Collection dedicated to brands, packaging and advertising.