Question: when did the sydney opera house became a world heritage site
Answer: 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 .