The Archives include important documents in the history of the United States, among them the Declaration of Independence, the Constitution and the Bill of Rights. Visitors can see all these documents enclosed in heavily fortified cases (which I believe go underground at night). There is also a copy of the 1297 Magna Carta confirmed by Edward I. I didn't go in as I have seen these documents several times, but walking around the neighborhood was pleasant; it's a part of Washington I rarely went to when living here.