Jestico + Whiles Architects has designed this earth-covered den-like building (below) for a playground dedicated to Diana, Princess of Wales in Kensington Gardens. The playground's £300,000 Home Underground is inspired by Peter Pan, whose author J M Barrie was a local resident and donated money to build a playground before he died. The oval Teletubbiesque building built into a mound has three rooflights and contains a park managers' office, first-aid centre and children's loos. Work is due to start on the 120m x 60m park this month for a summer finish. Other features include a tree house and sand pit with beached ship. The project for the Royal Parks Agency is being run by environmental planners Land Use Consultants.