Alexander Calder’s mobile sculptures, constructed from tin and wire, transformed the field of modern sculpture. Calder’s mobiles developed out of his famous ‘circuses’ of animated wire figures, which were conceived in a playful spirit with a living dynamism and balance evoking music or dance. Calder’s tin mobiles possess a delicate sense of form and colour and are perhaps best seen as plastic equivalents of Joan Miró’s paintings, which Calder admired for their whimsy and grace. Conceived on a domestic scale, Petit Château fort is a standing mobile sculpture that moves with gentle kinetic force.