 A project on Hawaii's Kauai Island, and it's not your average billionaire's retreat. But the Zuckerberg Real Estate saga doesn't stop there. The family also owns homes in Palo Alto, California. In a quiet part of Kauai, Hawaii, a big construction project is happening. It is Mark Zuckerberg's deal, but it's super hush hush. Behind a tall wall, away from the road, workers are busy. Security guards keep watching trucks go in and out with their supplies. People working there can't talk about it. There are very strict rules. Some even got in trouble for sharing stuff on social media, but can you be surprised? The project is massive, covering a big chunk of the island. It includes a huge underground shelter, its own power and food, and costs estimated over $270 million.