One of the reasons why the Sony Center makes such an impact (apart from the 5:1 plot ratio excluding below ground) is its extensive use of glass facades, which were very unusual in Berlin until recently, glass being confined by regulation to windows. All that has changed, and ingenious use has been made of glazing, behind which sits evidence of previous buildings on this key site (which had the first major railway station in Germany, built in 1838, and later the first traffic light, now recreated).The conservation approach is in respect of the Esplanade building, now partly reconstructed, which involved raising a chunk of the building 2.5 metres and moving it 7 metres - at a cost of DM5 million (£1.55 million). How about conserving buildings within glass boxes if it allows useful development above? A point pondered by Michael Aukett in a Sony Center cafe, who is faced with the dilemma of how to deal with a listed but redundant cinema at Clapham Junction, where he has designed a major new mixed-use scheme. It would be easier to get permissions in Berlin.