How they hid the cauldron in the roof
The maker of the cauldron in which the Olympic flame burns throughout the Games has lifted the lid on some of the secrets of its positioning.
Organisers of the opening ceremony hid the huge cauldron behind the roof during the cultural performance to make sure nothing would obstruct views of the stadium from above or below.
Then, in the first 16 minutes of the Parade of Nations during which Olympic athletes walked into the arena, the cauldron was slid 31 metres along rails on the roof to position it for the highlight of the night - Li Ning's lighting.
Wang Wenli of the cauldron's manufacturer, Shougang Steel Group, said the firm chose that moment because the roof was dark and attention was on the athletes.
'So when the lights were turned on again, everyone was surprised to see a huge cauldron right there,' Mr Wang said. 'Many of us burst into tears when the cauldron was lit because it was really a hard task for all of us involved to make it happen.'
It took Shougang seven months to build the 32-metre-diameter, 45-tonne structure. It lifted the cauldron onto the 'Bird's Nest' last month and tested it several times at night to make sure the 'national secret' did not leak out.
Thousands of rivets, more than 1,000 steel sheets and more than 2,000 lengths of steel pipe were used to build it.
Like all other procedures and projects for the opening ceremony, there was little margin for error. 'We paid extreme attention to even tiny details to make sure this product was of the highest quality,' Mr Wang said.