Democratic presidential candidate Senator Barack Obama (D-IL) listens to testimony from General David Petraeus and Ambassador to Iraq Ryan Crocker to the Senate Foreign Relations Committee on Capitol Hill in Washington April 8, 2008. REUTERS/Joshua Roberts

MOUNT RUSHMORE NATIONAL MONUMENT, South Dakota, May 30 (Reuters) - Even in the middle of a fierce presidential campaign, Barack Obama couldn’t resist the opportunity to go on a field trip.

When the Democratic White House hopeful heard the press corps and some staff members were planning a late-night trip to see Mount Rushmore National Monument, he decided he didn’t want to be left out.

So, shortly after arriving in South Dakota after an evening campaign rally in Montana, Obama made the 30-minute car trip to see the monument, of four presidents chiseled into the side of a massive granite outcropping.

After a park ranger gave him a private explanation of the national monument, Obama noted that his daughter Malia had told him she had gone on a field trip on Friday. “I had one too,” he said, as he walked away from the flood-lit monument.

He laughed when asked if he could imagine his face chiseled into the granite some day.

“I don’t think my ears would fit,” he said. “There’s only so much rock up there.”