Ai Weiwei and Herzog & de Meuron reveal 2012 pavilion plans A floating platform roof, which will be raised about waist-high above the ground will collect rain water to reflect the skies. It can also be drained "like a bath tub" so that dance performances to take place on the roof. Herzog & de Meuron, the Swiss architects behind the Tate Modern, have never worked with Ai Weiwei in the UK before. In a statement, the collaborative artist-architect team said the central theme of the design is the layers of history hidden into the earth, where remnants of the previous 11 pavilions lie. Their shape varies: circular, long and narrow, dots and also large, constructed hollows that have been filled in... These remains testify to the existence of the former Pavilions and their greater or lesser intervention in the natural environment of the park. Another key feature will be a giant rain gauge, which the design team call "a kind of well, to collect all of the London rain that falls in the area of the Pavilion." "In that way we incorporate an otherwise invisible aspect of reality in the park - the water under the ground - into our Pavilion," they said. Previous architects who have been invited to take part in the commission include Zaha Hadid, Daniel Libeskind with Arup, and Jean Nouvel. Alongside the Pavilion this summer, the Serpentine Gallery will host a major exhibition of the work of Yoko Ono.