The 2012 Serpentine Pavilion, designed this year by Swiss firm Herzog & de Meuron and Chinese artist Ai Weiwei, opened to the public this weekend.
Avoiding the bombastic scale that has characterised recent pavilions (particularly Frank Gehry's in 2008 and Jean Nouvel's in 2010) this year's effort goes underground, with a pit dug out of the Serpentine's lawn, creating a sunken amphitheatre clad in cork, and covered by a wide, thin disc filled with water.
The taint of minor architectural controversy hangs over the project. The designers promised an 'architectural dig' that would uncover the foundations of previous pavilions and incorporate them into the new one. That isn't what happened in practice: the outlines of earlier foundations have instead been recreated, with a dozen columns holding up the roof, each representing one of the earlier incarnations.
Does the sleight-of-hand matter? Not really. Visiting on a warm Saturday afternoon the pavilion looked to be a hit, with children and dogs alike taking pleasure from scrambling around the labyrinthine interior.
In selecting this year's designers, the Serpentine has cheated slightly on its rules; each year's project is supposed to be designed by an architect who has never built in Britain before, which is not the case for Herzog & De Meuron, who completed Tate Modern the same summer that the first Pavilion opened. However, it is their first British project with Chinese artist Ai Weiwei, and it is into his work, with its focus on ghosts and memory, that the Pavilion most obviously fits. Unfortunately, he's unlikely to see the finished product: Chinese authorities have confiscated his passport, and he was forced to collaborate with his Swiss partners via Skype.