'Heartbreak' hill could decide medals
The cream of the world's triathletes have spent the last year thinking about "the hill" and wondering how much of an impact it will have on the two Olympic races.
Appearing in the Games for the second time, the triathlon women go off first on Wednesday with the men racing the 1500 metre swim, 40km bike, 10km run combination on Thursday.
With drafting - sitting in the slipstream of the bike in front - being a legal part of the cycling leg at elite level, many top races become something of a procession with the places being sorted out on the run.
But the Athens course contains a tough 700 metre hill which the riders will have to tackle five times and which could be enough to break up the field.
That is what happened to the men in last October's World Cup test event on the course, even though the lead women's pack managed to stay together.
With both races wide open, everybody will be desperate to come out of the choppy sea swim in touch with the main pack going into the bike ride.