<P> The building and its surrounds occupy the whole of Bennelong Point on Sydney Harbour, between Sydney Cove and Farm Cove, adjacent to the Sydney central business district and the Royal Botanic Gardens, and close by the Sydney Harbour Bridge . </P> <P> Though its name suggests a single venue, the building comprises multiple performance venues which together host well over 1,500 performances annually, attended by more than 1.2 million people . Performances are presented by numerous performing artists, including three resident companies: Opera Australia, the Sydney Theatre Company and the Sydney Symphony Orchestra . As one of the most popular visitor attractions in Australia, more than eight million people visit the site annually, and approximately 350,000 visitors take a guided tour of the building each year . The building is managed by the Sydney Opera House Trust, an agency of the New South Wales State Government . </P> <P> On 28 June 2007, the Sydney Opera House became a UNESCO World Heritage Site; having been listed on the (now defunct) Register of the National Estate since 1980, the National Trust of Australia register since 1983, the City of Sydney Heritage Inventory since 2000, the New South Wales State Heritage Register since 2003, and the Australian National Heritage List since 2005 . </P> <P> The facility features a modern expressionist design, with a series of large precast concrete "shells", each composed of sections of a sphere of 75.2 metres (246 ft 8.6 in) radius, forming the roofs of the structure, set on a monumental podium . The building covers 1.8 hectares (4.4 acres) of land and is 183 m (600 ft) long and 120 m (394 ft) wide at its widest point . It is supported on 588 concrete piers sunk as much as 25 m (82 ft) below sea level . </P>

When did the sydney opera house became a world heritage site