Wolfenstein 3D: Ep1 Floor 1 - All Secrets + Extra Life + Secret Floor Location 

There is a SECRET DOOR to a SECRET LEVEL in the very first floor of the very first episode of Wolfenstein 3D (Escape From Wolfenstein).
I'll show you where. And on our way I'll teach you the location of 5 SECRET ROOMS and an EXTRA LIFE. Well... actually... 2 EXTRA LIVES.
Come with me.