Underground Shelter: The most discussed feature is a 5,000-square-foot underground shelter. Planning documents reportedly show it includes living space, a mechanical room, and an "escape hatch." The door is described as being made of metal and filled with concrete, similar to those in bomb shelters.  

Zuckerberg's Response: While media reports and investigations have labeled this a "doomsday bunker," Mark Zuckerberg has publicly downplayed this. In a recent interview, he stated, "I think the whole thing got blown out of proportion," and described the structure as a "little shelter" or "basement."  

Compound Features: The shelter is part of a much larger, 1,400-acre complex. Reports, citing building plans, indicate the compound includes two main mansions connected by the underground tunnel, at least [suspicious link removed], a gym, pools, a sauna, a cold plunge, and even a [suspicious link removed] connected by rope bridges.  

Self-Sufficiency: The property is designed to be self-sufficient, with its own large water tank and pump system, as well as extensive agriculture and cattle ranching.  

Secrecy and Controversy: The project is known for its extreme secrecy, with all workers reportedly bound by strict non-disclosure agreements (NDAs). It has also been controversial among some locals for its scale and the impact on the community.

(http://www.autoadmit.com/thread.php?thread_id=5798127&forum_id=2Firm#49431377)