Chicago is home to some of America's most iconic paintings such as Edward Hopper's Nighthawks and American Gothic by Grant Wood, both to be found in the collection of the Art Institute of Chicago, but in 2006 a work by an Indian-born British artist was unveiled in Millennium Park which has come to symbolise the city. Rosalind Whyte discusses Cloud Gate, a sculpture by Sir Anish Kapoor, affectionately known by locals as 'The Bean'.