Rain Circus is the project of an innovative flexible water tank serving educational gardens. Created in collaboration with HPO, it won the special mention at "Premio Federico Maggia 2022" award. The project idea was born from a workshop with teachers and students of the "Ex-Redentoristi" school in Biella, Italy. We focused on collecting rainwater without interfering with the configuration of the existing gardens. We decided to use a water collection bladder, a coloured "balloon", fixed on top of the garden hill, whose resistance and elasticity allows children to play and walk on it. The water collection system works by drainage with gravel, positioned on base of the inflatable tank. The filtered water is stored and redistributed through an underground system. Two crank pumps allow the access to water without using electricity.