1. An Indoor Swimming Pool
One of the most luxurious things you could ever do with a basement is to create an underground indoor swimming pool. You are guaranteed to never get a sunburn swimming in your pool this way. The obvious benefits of having an indoor swimming pool are that it will be temperature controlled, so you can go swimming even in the dead of winter. There is also no chance that your neighbors could potentially peek over the fence to see you in your bikini.
However, this would not be possible in places with a high water table. There are only certain geographical locations where you would be able to create a basement pool. And, of course, it is outrageously expensive. According to Home Adviser, building a pool in your basement would cost between $20,000 and $100,000.