If I had way too much money I would have a huge underground complex, with video game arcade, retro gaming area (with CRT TVs), pinballs, PC LAN area, home theater, PC lab desk, electronic and DIY workshop, servers room, kitchen, food storage, bathroom, bedrooms, survival material storage, self sufficient power generation, communication equipment with several alternative and backups (FTTH, 5G, copper wire, mesh radio), surveillance system to check the decoy/day house while undergound and more stuff probably that I cannot think of right now.

All of this hidden below a slightly above average size house, it will be the day house but more like a decoy house as I will spend most time underground.