Moscow City Tower is to be Europe's tallest and the world's second tallest building. The 600-m naturally ventilated tower designed by Norman Foster will accommodate 25 000 people - a city unto itself - and the designer is aiming for LEED gold accreditation. The internal temperature will be maintained at 21°C in winter and 23°C in summer and the building is designed to cope with extremely cold temperatures in winter and temperatures of around 26°C in summer. The tower will feature an "energy highway" that will transfer waste heat from the commercial and office areas to the hotel and residential floors. Secondary energy pathways will transfer energy horizontally to pre-heat ventilation air and domestic hot water and to provide low-grade heating of underfloor systems. The building will have no boilers and will draw on waste heat from an adjacent cogeneration plant via Moscow's district heating system. Over 60 air-handling units will supply fresh air and summer precooling will be performed using pipework embedded in the concrete basement walls. Photovoltaic cells on the tower's mast will power the external lights.