Watching a movie where they have a safe room, you might get a few misconceptions. Since the main purpose of safe rooms that most install is to protect them against a home invasion, you want to make sure that it is close to the area where you are most likely to be at the time. Having one in the basement isn’t safe, since you would be unable to get there if there was an intruder in your home on the ground floor. It is also important to consider the air, water and, food supply if you were to stay in there for an extended period of time. Having a method of communicating with the outside would also be very important.
If you want to install a safe room, you also need to ensure that there is sufficient support underneath where you have it installed, since it could be quite heavy if it is built to last.