Congratulations to Robert Sansome of Sansome Hall Architects, who spotted the three changes we made to the building on the right, Jørn Utzon's Sydney Opera House. For the chance of winning a bottle of champagne, readers are asked to spot the deliberate alterations we've made to the building on the left, Le Corbusier's Villa Savoye. Clue: there are four changes. Post your answers, to arrive by first thing Monday morning, to AJ Ring the Changes, 151 Rosebery Avenue, London EC1R 4GB, or fax 020 7505 6701. The first correct entry pulled out of the hat wins the bubbly.