Olympic mystery: Where is the London cauldron?

London's Olympic Stadium is ready, with a pristine track, a well-manicured grassy field and rows of gleaming seats to welcome 80,000 fans. But one thing is clearly missing.

Where's the cauldron that will hold the Olympic flame?

Organizers usually keep back details about the Olympics' opening ceremony, including the flame lighting, to ensure the appropriate drama, so it's no surprise that they're being coy. But usually there is some structure — somewhere — that indicates where the flame will burn throughout the games.

There is one tower next to the Olympic Stadium that could solve the mystery — the ArcelorMittal Orbit, a ruby red sculpture of twisted steel that looks like a smashed rollercoaster. Except that Olympic officials say this crazy sightseeing contraption won't be it.

"No, it's not the cauldron," said Peter Tudor, the director of venues for the Olympic Park Legacy Corp. "I would know if there was a massive gas pipe inside."

Well, if it isn't there, then where? The question has become as much of the mystery as the opening ceremony itself.

In the ancient games, Greeks lit a ritual fire to commemorate Prometheus and his theft of fire from Zeus. Then at the 1928 Amsterdam Games, a cauldron was lit — although no one is quite certain about how that came about, said Bill Mallon, co-founder of the international society of Olympic history.

But fire really took hold at the Nazi-backed 1936 Berlin Olympics. Chief organizer Carl Diem came up with the idea of a relay starting at Olympia in Greece, and a tradition was born. Torchbearer Fritz Schilgen was chosen to light the cauldron because he was a good looking guy — a theme repeated in 1948 when the dashing John Mark took the flame in London.

Mallon said the cauldron lighting really became a wow moment at the 1952 Summer Games in Helsinki. The Flying Finn, Paavo Nurmi, one of the best long- and middle-distance runners ever, brought the flame into the stadium and Hannes Kolehmainen, another Finnish long-distance great who competed in 1912 and 1920, lit the cauldron. The combination of local heroes and fire proved lasting.

After that, Olympic organizers stayed up late at night trying to figure out how to outdo the games before. Some memorable moments:

— An archer at the 1992 Barcelona Olympics lit the cauldron with a flaming arrow.

— In Atlanta in 1996, Muhammad Ali, who suffers from Parkinson's disease, held the torch high and bent over to light a wire that led to the cauldron — his arm shaking but his resolve firm.

— At the 2000 Sydney Games, gold medalist Cathy Freeman lit a ring of fire in a pool of water.

Given the pressure, it's unlikely the British will go for some sort of virtual cauldron, however Earth-friendly or sustainable that might be. Historians like Mallon puts its apparent absence to the fact that the London organizing committee plans to outdo the theatrics of other games.

"There will be a cauldron," Mallon said. "I'll betcha the cauldron will rise out of the stadium somewhere."