Millennium Dome. Night-time view of part of the Millennium Dome in London, England. This is the largest dome in the world. In the year 2000 it contained the Millennium Experience, a huge exhibition to celebrate the millennium. The exhibition had 14 themed zones on topics including business, religion and the body. The 2 mm thick roof (white/purple) is made of teflon-coated glass fibre fabric, supported by 70 km of steel cables attached to twelve 100 metre high masts (yellow, upper frame). Rainwater falling onto the roof is collected, filtered and stored for use in the Dome's toilets. The Dome is 320 metres across and can hold 40,000 visitors.