I heard a while ago that the Tomb of the Unknown Soldier had a very serious and lengthy crack in the marble that needed to be repaired. I wonder if this was ever completed.
I think it was repaired or they were trying to determine the best way to repair it. My memory....
“In June 2009 Arlington National Cemetery and The Army Corps of Engineers announced that the monument was to be repaired, not replaced. In 2010, the cracks were filled but the repairs lasted only a few months.  As of June 2011, the cemetery was struggling to repair the cracks in the monument, one of which measured 28.4 feet long, with another at 16.2 feet. In September 2011, the cracks were filled again and a 21 October 2011 inspection by the Army Corps of Engineers and other experts pronounced the repairs a success.”
There was a spirited debate here on FR several years ago on the issue of repairing or replacing the sarcophagus. FR search refuses to cough it up, however.
Here’s a photo sideshow of the recent inspection of repairs by the Army Corps of Engineers. Numerous repairs have been made in the past and all have been unsuccessful. I don’t expect any different outcome this time. Those cracks were evident 48 years ago when I was there.