A woman places a rose at the polar bear enclosure in Berlin zoo, March 20, 2011. Knut, the polar bear who became a global celebrity as a cute cub, died in Berlin zoo aged just four. Knut, the first polar bear born at the zoo for more than 30 years, was rejected by his mother and fed instead by his keeper Thomas Doerflein. Thousands of visitors came to watch keeper and cub playing together, and Knut's fame soon spread around the world. REUTERS/Tobias Schwarz