The O2 Dome
It's quite funny, when I started my elephant series, I planned to include the Dome as London's largest (white) elephant but events have overtaken me and it has since been rebranded "The O2" and has staged some pretty impressive concerts. To start with, I bridled at the blatant commercialism of the branding exercise, but actually, why not? It was only mouldering beforehand, and they've breathed new life into it. Good luck, say I.
Oh, and because I couldn't find the right clip for Private Frazier's "We're all doomed" catch phrase (which comes to mind each time I think of The Dome), here is a link to more Dad's Army clips than you can shake a stick at.