The showpiece of the 2008 Summer Olympics was the Beijing National Stadium, nicknamed "The Bird's Nest" because of its nest-like skeletal structure. The stadium hosted both the opening and closing ceremonies, as well as the athletics competition. Construction of the venue began on 24 December 2003. The Guangdong Olympic Stadium was originally planned, constructed, and completed in 2001 to help host the Games, but a decision was made to construct a new stadium in Beijing. In 2001, the city held a bidding process to select the best arena design. Several criteria were required of each design, including flexibility for post-Olympics use, a retractable roof, and low maintenance costs. The entry list was narrowed to thirteen final designs. The bird's nest model submitted by architects Jacques Herzog and Pierre de Meuron in collaboration with Li Xinggang of China Architecture Design and Research Group (CADG) was selected as the top design by both a professional panel and by a broader audience during a public exhibition. The selection of the design became official in April 2003. Construction of the stadium was a joint venture among the original designers, project architect Stefan Marbach, artist Ai Weiwei, and a group of CADG architects led by Li Xinggang. Its $423 million cost was funded by the state-owned corporate conglomerate CITIC and the Beijing State-Owned Assets Management Company.