They don't know where exactly that's why it's called "tomb of the unknown."
The monument is also named 'The Tomb of the Unknowns' and (I believe) contains the remains of several soldiers, from several theatres of war. They are all recipients of distinguished service medals and died in the thick of it. Plenty of good information at the Arlington web site. Thanks for asking and I hope you can get there.
I have been to Arlington. Seen the changing of the guard at the tomb. If people get to DC They should get there to see it
Somewhere close to Chalons-sur-Marne, France,
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