https://redstate.com/bobhoge/2026/05/31/what-lies-beneath-massive-secret-vault-under-lincoln-memorial-to-be-opened-to-the-public-for-america250-n2202908
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Something you presumably didn’t see on your visit, however, is a massive 50,000-square-foot foundation built to keep the whole thing from sinking into the swamps of D.C. It’s called the Undercroft, and it’s been a tightly held secret for decades. In June, the Department of the Interior will invite the public to see the hidden vault, Secretary Doug Burgum announced Sunday.."
