The Hidden Cave Beneath the Lincoln Memorial

The Lincoln Memorial is one of the most visited monuments in the world - but nearly every visitor has been walking above a secret. Beneath the pink Tennessee marble lies a vast cave-like basement the public has never been able to enter, until now.

A Basement Bigger Than the Building Above It

The undercroft of the Lincoln Memorial spans 43,800 square feet, making it nearly twice the floor space of the marble memorial above. It stands three stories tall, its ceiling supported by 122 massive concrete columns that sink roughly 65 feet to bedrock. The columns were essential: the memorial sits on formerly swampy ground reclaimed from the Potomac River, and only by anchoring deeply into solid earth could engineers keep the 38,000-ton structure from slowly sinking.

A Cave That Grew Itself

After the memorial was sealed in 1922, the undercroft developed its own ecosystem. Rainwater seeped through the marble above, picked up calcium deposits, and began dripping from the ceiling - forming real stalactites. The space was eventually classified as a genuine cave. When Interior Secretary Doug Burgum visited before the opening, he noted simply: "They're still dripping."

The Workers Who Left Their Mark

Construction ran from 1914 to 1922, and laborers left something behind. On the concrete columns, workers sketched cartoons - including drawings of Mutt and Jeff, the characters from the first daily newspaper comic strip. Those sketches survived over a century in the sealed chamber and are now protected behind plexiglass. One worker signed his cartoons "Bosco Johnny" on a nearby column.

Opening After 112 Years

The undercroft ran limited public tours between the 1970s and 1989, when asbestos was discovered and access was cut off entirely. A $69 million renovation - funded in part by philanthropist David Rubenstein and the National Park Foundation - transformed it into a proper museum. The new exhibit space covers 15,000 square feet, with floor-to-ceiling glass panes letting visitors look out into the original structural undercroft and its 122 columns stretching into the dark. The museum opens June 25, 2026, as part of America's 250th anniversary celebration. Timed-entry tickets are free and available at recreation.gov or by calling 877-444-6777.