The Thirteenth Floor

The Thirteenth Floor (1999)

This is one of my favorite science fiction movie.
Why is this movie called the thirteenth floor?
I didn't get it when I first saw this movie.

Then I found that there are some buildings doesn't have the thirteenth floor.
Since the number is an unluck number, some of the hotels don't have this floor.

It is very similar to the number 4 in chinese culture.
We also found that there is no such room whose number is ended with 4 in many hotels.

It's very interesting and weird.