Shenzhen is the cradle of China's interior design industry. The city now has more than 2,500 interior design firms employing more than 30,000 people. The industry's annual revenue has reached 1 billion yuan and is enjoying annual growth of at least 25 percent. The interior design industry in Shenzhen is the most fully-fledged in China, capable of offering complete solutions. Its related industries also provide employment opportunities for tens of thousands of people. The China (Shenzhen) International Interior Design Festival, which is held in November each year, has been held five times, with the number of participants growing from 30,000 to nearly 350,000 last year. Shenzhen designers have provided interior design for landmark buildings in most Chinese cities, including the "Water Tube," the "Bird's Nest," the new CCTV tower and the National Grand Theater.