Congratulations to Joanna Morland of Portland, Dorset, who managed to spot all eight changes we made to the building below, Schröder House in Utrecht. For the chance of winning a bottle of champagne, readers are asked to spot the deliberate changes we've made to the building above, Scharoun's Berlin Concert Hall. Clue: there are five changes. Post your answers, to arrive by first thing Monday morning, to Ring the Changes, 151 Rosebery Avenue, London EC1R 4GB, or fax 020 7505 6701. The first correct entry pulled out of the hat wins a bottle of bubbly.