Apparently there is an under ground emergency communication center and bomb shelter called "Orange One."

When President Nixon decided to add a swimming pool outside the Aspen Lodge, the location he selected was directly over the bomb shelter. "Orange One", as it was called, had to be reinforced for a cost of $261,000

It's a "presidential relocation site."

A 1994 article in Mother Jones Magazine describes the preparations required to conceal the work on the underground command center when Soviet Leader Nikita Khrushchev was scheduled to visit Camp David:

"Laborers worked night and day to haul truckloads of dirt and stone, making sure to hide every trace of their excavations before Khrushchev's arrival. A large deck was constructed to conceal the cavernous hole. Little did Khrushchev know, as he stood smiling on the deck posing for photographers, that he was atop a presidential relocation site."

https://archive.vn/2u6D6