The O2 Arena , commonly known as The O2 , is a multi-purpose indoor arena in the centre of The O2 entertainment district on the Greenwich Peninsula in southeast London, England. It opened in its present form in 2007. It has the third-highest seating capacity of any indoor venue in the United Kingdom, behind Co-op Live and Manchester Arena, Manchester, UK , and in 2008 was the world's busiest music arena. As of 2022, it is the ninth-largest building in the world by volume with a diameter of 365 m