Undoubtedly the building that everyone will remember from London's Olympic Park will be the Aquatics Centre, designed by Zaha Hadid, and located at the gateway to the park where most people will enter. This makes it perhaps the most important building to get right, and in terms of architectural ambition it doesn't disappoint.
The building will house the swimming and diving events of the Olympics, as well as a further training pool, all of which will become community facilities after the Games. The design is dominated by a huge curving roof reminiscent of a wave of water or a swimmer doing butterfly, which is clad on the underside with timber and on top with recycled aluminium. In legacy mode it will seat 2500, but during the games capacity is vastly increased to 17500, with spectators seated in 2 huge temporary wings built on the sides.
My first thoughts are that the design is stunning, by far the best looking building on the site, and perfectly in tune with the flowing, organic nature of its context. Since the main route into the Olympic site passes right in front, I think this is absolutely the right move in terms of architectural impact - the render below shows the legacy view, with the roof extending over the main 'land bridge' into the park.
Unlike the main stadium, the Aquatics Centre has been built very much with legacy in mind - most of the released renders show what it will look like afterwards, which after all is far more important than what it will look like for the first few weeks of its life. To house the vast increase in spectators during the games, two giant 'bat' wings will be built on the sides (where the large glass walls are on the above renders).
These definitely compromise the elegance of the main structure, however I don't think that's really a problem - the architects have accepted the fact that some temporary facilities will be required, and designed them as such - they're obviously of a different architectural language. Whilst the downsizing idea has meant the stadium won't look right in either mode (Olympic or Legacy), the Aquatics Centre will be beautiful in legacy, and keeps much of its good points in Olympic mode (and anyway, most people will be watching the Games on TV, which will really only show the inside).
The inside is perhaps where the design is a little weaker, although to be fair there isn't much to go on as yet.
At least the underside of the roof should be spectacular, clad in pale timber, and flooded with light from the large windows. The games mode render on the right seems a bit claustrophobic, and I can imagine the view from the top of the temporary wings could be a little weird, as you won't be able to see across (only down to the pool). Let's hope they've improved on the alien light fittings in the right image as well!
But these issues aside, Hadid's Aquatic Centre is definitely architecture to get excited about - the structure alone is very impressive: the 160m long roof weighs 2800 tonnes, but is supported on just two concrete pillars and a short wall at one end, and was built on temporary steelwork then lowered into its final position. Although it actually appears quite small from some angles, the span is very impressive, as you can see in the photo below, which was taken a few months ago. At the time of writing, the roof steelwork has been completed, and is partly clad, with the pools taking shape underneath.
The Aquatics Centre is in many ways the exact opposite of the main stadium - the designers of the stadium have focused so much on its demountability that the design has almost become boring, whereas Zaha Hadid and her team have thrown caution to the wind and attempted something very exciting, although perhaps at the expense of the budget and the venue's sustainability. There's certainly a lot of steel used - compare the dense web of the roof construction with the simple frame of the stadium behind in the above photo - although the issue of downsizing after the Games has still been dealt with.
Overall, I think the architecture of the Aquatics Centre is very successful, following a much more suitable path than the stadium and dealing with downsizing in a much more thoughtful way, although of course big questions would be asked if every venue were as expensive as Hadid's building. Maybe each Olympic Park needs a 'showcase' building, and this is it for London.