May 31, 2026 / 9:27 AM EDT
/ CBS News
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To call Washington a "swamp" is a metaphor, but also the literal truth. So, when planning began for the Lincoln Memorial in the early 1910s, builders faced a real sinking problem. Their solution led to one of Washington's best-kept secrets, hidden for over a century … until now.Underneath the Lincoln Memorial is what's known as the memorial's Undercroft (a term usually reserved for the vaulted basement of a medieval castle or cathedral). Here, 120 massive concrete pillars sink 50 feet into the ground, down to the bedrock, to support the weight of the marble above.
The Undercroft, constructed to support the weight of the Lincoln Memorial above.
