Beneath a flawless blue sky with the air scented by pine leaves and the noise of cicadas in the background, the modern Olympics returned to their spiritual home with the men's and women's shot put qualifying competition.

The finals will be staged on Wednesday evening on the site of the ancient Olympics.

"It's an awesome experience," said Heaston, who added that she had thoroughly enjoyed the experience despite failing to qualify for the final. "I think I could have done better but I will take the experience.

"But I needed to think about what I was doing in the ring rather than what I was doing in history."

Another non-qualifier, Greek Kalliopi Ouzouni endorsed Heaston's sentiments.

"I feel so small being in this ancient place where the Olympic Games started," she said.

Responding to shouts of "Go Kiwi" from a section of the crowd who started streaming into the arena shortly after sunrise, New Zealand's Valerie Adams was the first to qualify automatically with a mark in excess of 18.50, launching the shot 18.79 metres to finish third in her group.

Belarussian Nadezhda Ostapchuk was the leading qualifier with 19.69 metres, followed by Russian's Olympic champion Irina Korzhanenko who recorded 19.43. Germany's 1996 Atlanta Olympic champion Astrid Kumbernuss, who has been troubled by injury, failed to advance.

American men's champion Adam Nelson fouled his first attempt but compensated with his second, hurling the shot well past the required 20.40 metres to record 21.15, the morning's leading mark.

His team mate John Godina, the three-times world champion, also qualified but hopes of an American clean sweep were dashed when Reese Hoffa missed the cut.

Nelson immediately quit the competition but still found time to share his thoughts on competing in ancient Olympia.

"This exceeds all expectations," Nelson told reporters. "It's better than anything I could have dreamed.

"There is something special about this place. The ruins are pretty amazing. It's a reminder of where it all began."