O2 - I've always known it as 'the Dome' - is a fascinating structure, easily visible from the air to incoming flights, and now hosts a variety of exhibitions and events.
We went to see 'Body Works' a collection of plastinates (cadavers, and some animals and birds, preserved and impregnated with plastics) graphically displaying the various systems of the body. Gruesome-sounding, it was actually interesting, informative and sensitively mounted. Also controversial. Wikipedia covers it.