The last few touches to the Millennium Dome's external structure have just been completed with sealing of the roof around the masts and installation of rainwater outfalls. Numerous external works are now being built including smaller buildings such as the 'Baby Dome'. Thames Water is also providing a recycling facility on site for run-off which will be used for non-potable functions such as toilets and fire hydrants in the six 'core' service buildings. These structures are being built by Watson Steel and have common facilities such as restaurants for the estimated 12M visitors in 2000. Each building is already topped by two distinctive giant horizontal tubes, 2m in diameter, for Dome ventilation intakes. Air extraction is through fans in the pylons. Under way in the centre of the 320m diameter covered space, already surrounded by a glazed boundary wall, are the foundations and steel frames for the central arena, including an extending telescopic stage which will rise towards the roof. Foundations and steel shells for seven of the 14 exhibits are also under way.