Bill Gates has a nice house. We all know that. But what we don't know is how incredible it actually is on the inside. There are tons of secrets we don't quite know, until now. From customized temperatures to him having a favorite tree, there's more. Check it out:

1. It took Gates 7 years and $63 million to build his estate in Medina, Washington, and he named it “Xanadu 2.0,” after the estate of Charles Foster Kane in the movie “Citizen Kane.” The house is a massive 66,000 square feet, and it’s completely decked out in high-tech intricacies. Here are some of the top features.

2. It’s worth $123 million now, but Gates purchased the lot for $2 million in 1988.

3. It took half a million board-feet of lumber to complete the house. It was built with 500-year-old Douglas fir trees, and it took 300 construction workers to build it-100 of which were electricians.

4. Gates has a favorite tree on the property, and it’s electronically monitored 24 hours a day. If at any point it becomes too dry, water is pumped into it automatically.

5. 23 cars can be housed altogether in Gates’ garages. He’s got several throughout the property. The most fascinating one is an underground cave made of concrete and stainless steel. That one alone can hold 10 cars.

6. The natural surroundings reduce heat loss in the home.Gates took a page from the Hobbit book and made the house ‘earth-sheltered,’ meaning it’s built into its surroundings to help regulate temperature.

7. The library is 2,100 square feet and is equipped with a dome roof and 2 (count em, 2) secret bookcases, including one that has a hidden bar. On the ceiling is a quote from “The Great Gatsby” that says “He had come a long way to this blue lawn, and his dream must have seemed so close that he could hardly fail to grasp it.” Also living in the library is a Codex Leicester, a 16th-century da Vinci manuscript that Gates bought for $30.8 million.

8. The pool is located in its own 3,900 square foot building. Swimmers in the pool could swim underneath a glass wall that will lead them to a terrace on the outside. Oh yeah, and there’s also an underwater music system.

9. Gotta pee? The house has 24 bathrooms, 10 of those being full baths.

10. The artwork on the walls changes with the press of a button. All over the house are $80,000 worth of computer screens, and anyone can change the screens to display their favorite artwork or photograph, which are stored on $150,000 devices.

11. The sand on Gates’ private beach is delivered by barge from St. Lucia every year.

12. If you like to bounce, Gates has a room just for you. Equipped with a 20-foot ceiling, the room houses a giant trampoline. There’s no word on how big it is, but it’s got its own room, so… you do the math.

13. 200 guests can be entertained in the 2,300-square-foot reception hall. One wall has a 6-foot-wide fireplace, and another has a 22-foot wide video screen.

14. Hungry? There’s 6 kitchens, each in different parts of the house so staff can prepare for any event.

15. Climate and lighting are monitored for each guest with a high-tech sensor system. When a guest arrives, they get a pin that connects with sensors all over the house. The guest enters their temperature and lighting preference so that when they move from room to room, the settings change. Speakers behind the wallpaper also let music follow you from room to room.

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