The structure originally cost £700,000,000 of taxpayers money and was infamously known as the Millennium Dome except it was a colossal cock up because nobody knew what to put inside it after it was built. At first they threw in a fairground and some architecture nonsense but they had a real time filling it because it was the size of two football pitches. Was a far cry from the London Eye in terms of a tourist attraction.
From it's opening week back in January 2000 and this was as good as it got
In 2005 AEG obtained the Dome for free from the British Government in return for a share of the profits. o2 secured naming rights early on and have a deal in place going until 2027 at roughly £12.5m a year. The structure is now a highly profitable multi-purpose venue holding up to 20,000 people from music to sports to theatre and other general entertainment. There's also bars and restaurants on site as well as commercial rooms.
The roof is a total shitshow - not sure what it's made of but probably some form of fiberglass sheeting. Now would probably be a good time to put a new sustainable one on but having said that, I wouldn't want it to lose its iconic look even if it's nothing more than glorified tent.