Mark Zuckerberg at Meta Connect.MetaMark Zuckerberg is building a 1,400-acre compound in Kauai, Hawaii, with a vast basement.Plans for the compound show an underground structure nearly double the size of the average US house.In an interview with Bloomberg, Zuckerberg said it was only a "little shelter" for hurricanes and the like.Mark Zuckerberg said the 4,500-square-foot underground structure in his Hawaii compound is just a "little shelter."The description was in answer to the question of whether he is building some kind of armageddon shelter as part of his 1,400-acre property on the island of Kauai.In a video with Bloomberg's "The Circuit" released on December 19, Zuckerberg effectively said the project was nothing to write home about.Bloomberg's reporter, Emily Chang, asked if Zuckerberg was entering his "billionaire era" with the Hawaiian home.(Business Insider in April calculated Zuckerberg's property holdings were worth about $200 million, spanning compounds in Palo Alto, Lake Tahoe and Hawaii.)"The Kauai thing is really fun," Zuck responded.