3D interactive artist Joe Hill poses with one of his works as part of the VisitBritain tourism campaign at Circular Quay on September 6, 2011 in Sydney, Australia. (Photo by Mark Metcalfe/Getty Images)

A rider demonstrates Lighting artist Bruce Munro latest installation “Star-Turn” at a one-night event in front of the Holburne Museum on December 21, 2011 in Bath, England. (Photo by Matt Cardy/Getty Images)

A Fiat 500c is unveiled at the New York International Auto Show April 21, 2011 in New York City. The New York Auto Show is one of the largest auto shows in the country. (Photo by Ramin Talaie/Getty Images)

Wai Ching Jason Poon of Hong Kong competes in the Men's 1m Springboard preliminary round during Day One of the 14th FINA World Championships at the Oriental Sports Center on July 16, 2011 in Shanghai, China. (Photo by Feng Li/Getty Images)

The Prague astronomical clock, or Prague orloj, is a medieval astronomical clock located in Prague, the capital of the Czech Republic. The clock was first installed in 1410, making it the third-oldest astronomical clock in the world and the oldest one still working.