Widely considered to be one of the most significant cultural figures of his generation in China and internationally, Ai Weiwei successfully occupies multiple roles as a conceptual artist, architect, curator, designer, film-maker, publisher and activist. Ai collaborated with Swiss architects Herzog & de Meuron as the artistic consultant on the Beijing National Stadium for the 2008 Olympics. As a political activist, he has been highly and openly critical of the Chinese Government's stance on democracy and human rights. He has investigated government corruption and cover-ups, in particular the Sichuan schools corruption scandal following the collapse of so-called "tofu-skin schools" in the 2008 Sichuan earthquake. In 2011, following his arrest at Beijing airport on 3 April, he was held for over two months without any official charges being filed; officials alluded to their allegations of "economic crimes" (tax evasion).