An Army honor guard watches over the Tomb of the Unknown Soldier day and night, summer and winter. They never crack.
But the tomb has. Two cracks run about three quarters of the way around it, and they may soon go completely through the massive solid block of marble.
"We cannot as custodians allow this condition to continue without doing something to remedy it," said Thomas Sherlock, the Arlington National Cemetery historian.
In Colorado, retired car dealer John Haines had an idea: He'd give the government a 60-ton marble slab from the same Colorado quarry as the original. Haines said he'd even pay for the carving and transportation -- in all, more than $60,000.
"I thought, 'Hey, no-brainer: I can donate that,' " Haines said.
That was five years ago. Haines ran into something as difficult to move as … well, as a 60-ton rock -- Washington bureaucracy. His offer is still being reviewed by at least six different offices.
"I may die before this happens, you never know," he said. "How can it be so difficult to try to give the country that you love and you live in a donation to try to help them improve one of their national memorials?"
The first unknown soldier -- from World War I -- was laid to rest beneath a flat marble slab in 1921. The big marble marker with the inscription, "Here Rests In Honored Glory An American Soldier Known But to God," was added in 1932.
Now, in front of the original soldier, crypts for unknowns from World War II, Korea and Vietnam were added -- though the Vietnam crypt is now empty, because the "unknown" was identified using DNA in 1998 and returned to his family.
Advances in forensic technology, like DNA analysis, mean there probably will never be another unknown soldier -- an anonymous warrior representing all the others fallen in battle.
Sherlock said that adds to the tomb's significance.
"Because we will not have another unknown," he said, "there will not be a place for people to come to remember the commonality of a war."
ABC News' John Yang and Matt Hosford reported this story for "World News Tonight."