Largest underground house

Microsoft billionaire Bill Gates (USA) lives in a vast earth-sheltered mansion overlooking Lake Washington in Medina, Washington, USA. Designed by architects James Cutler and Peter Bohlin, the building, much of which is concealed underground, occupies 6,100 m² (66,000 ft²) of space and was completed in 1995. It contains seven bedrooms, 24 bathrooms, six kitchens, an 18-m (60-ft) swimming pool, a 230-m² (2,500-ft²) gym, trampoline room and complex computer-managed environmental, data and entertainment system. Included in the £30-million ($60-million) cost of the building were 64 km (40 miles) of fibre optic cables and a team of up to 300 electricians to hook up the state-of-the-art electronics features.