Friction between grains of sand cause a curious "singing" sound.

The Cathedral of Salamanca has a number of unusual carvings but none so surprising as a modern astronaut.

An eccentric garden of sculptures crafted in India decorate an Irish green space dedicated to Alan Turing.

A seemingly endless landscape of pure salt stretches far across Bolivia.

A dismembered holy head stares out from her beautiful reliquary at the St. Dominic Basilica.

The World Wide Web was created in this nondescript corridor at CERN.

An unrealized dream to wirelessly electrify the entire Earth.

This innocent-looking townhome is actually a subway exit.

This upscale streetwear store is hidden behind a fake Snapple machine in the back of a deli.

The only parking meter in the entire town, it is surrounded by 100 free spaces.

One of New York's best collections of pinball is hidden in a secret bar in the back of this laundromat.

Hidden in plain sight on a pair of Manhattan subway tunnels are a pair of public instruments that sing to each other.

This secret Swiss fortress is disguised as a harmless pink house, complete with fake windows.

Leave the wardrobes and sweets to British schoolchildren, Shanghai's got a Coke machine that leads to booze.

A pedestrian island in the middle of world-famous Times Square emits a strange (and purposeful) humming noise.

The beautiful tunnel that ran from the lobby to Penn Station is still hidden underneath 34th Street.

This abandoned caretaker's apartment is one of 13 left in the New York Public Library system.

The signs of a long buried road can still be found hidden beneath a London sewer grate.

This historic address is home to the beloved ball and is an almost totally empty building among the most expensive real estate in the world.

An abandoned jewel of a ballroom on the top floor of Australia’s busiest rail station echoes with the sounds of a bygone era.

Built as a gift to the hottest tastemaker of the time, these hidden quarters remain an Art Deco showpiece.

A secret hatch containing two parchments was discovered in this statue over 40 years after its installation.

An exclusive waiting room built for the royal family in the 1920s is hidden in Milan’s central station.

The famous facade of Grand Central Terminal hides a regulation tennis court, and it's not the first one.