Record-breaking swimmer Michael Phelps matched his Athens haul of six gold medals to take his overall Olympic tally to 12 - and stay on course for his target of eight Beijing titles.
Swimming traditionally dominates the first week of Olympic competition and Phelps' latest performance, with another world record, ensured the Water Cube continued to hold centre stage on the day that the track and field competition finally got under way at the nearby Bird's Nest stadium.
Across town at another of China's modern architectural wonders, protesters staged another pro-Tibet stunt, this time scaling the eye-boggling new headquarters of Chinese state television.
American Phelps is aiming to win eight golds in Beijing to eclipse fellow swimmer Mark Spitz's record of seven at a single Olympiad, the Munich games in 1972.
Phelps had become the most successful ever Olympian earlier this week by eclipsing the previous record of nine career titles.
He took his haul at Beijing's Water Cube to six by winning the 200m individual medley, shaving 0.57sec off his world record to post a time of 1 minute 54.23 seconds.
Hungary's Laszlo Cseh took second in a new European record time of 1:56.52, one-hundredth of a second ahead of American Ryan Lochte, who had earlier won gold in the 200m backstroke in a new world-record time.
"I just wanted to step on it in the first 50m a little bit and try and get out to an early lead," said Phelps.
"I knew that was a hard double for Ryan. I knew in the first half if I got a big enough lead I thought I could hang on and that's all I wanted to do."
While the giant Phelps has been the star of the opening week of the Games, the heavyweights of the track and field competition got their first chance to compete in the Bird's Nest.
In the men's 100m heats, US sprinter Tyson Gay and Jamaican speed pair Asafa Powell and Usain Bolt coasted through in the event considered by many to be the most prestigious in the Games.
Britain's Kelly Sotherton made a solid start to the heptathlon while in the women's 800m, Jennifer Meadows and Marilyn Okoro advanced to the semi-finals but team-mate Jemma Simpson missed out after finishing fourth in the opening heat.
Okoro was the most impressive, finishing second in her heat to former world and Olympic champion Maria Mutola in 1:59.01, while Meadows was third in her heat in 2:00.33.
The 27-year-old from Wigan, wearing a black ribbon on her vest in memory of her father, who died 10 weeks ago, said: "I felt really relaxed out there, kept the nerves in check and tried not to do anything stupid and just bided my time."
Away from the sporting arena, Briton Philip Kirk, 24, from St Albans, Hertfordshire, was among five protesters arrested for a pro-Tibet stunt at the brand new offices of China's state broadcasters.