Olympia is an exhibition centre, event space and conference centre in West Kensington, London, England.Opened in 1886 as the National Agricultural Hall, it was built by Andrew Handyside and Company of Derbyand covered an area of 4 acres (16,000 m2). The Grand Hall, 450 feet (140 m) in length, by 250 feet (76 m) in breadth, was said to be the largest building in the United Kingdom covered by one span of iron and glass.