Serious Sam Easter Egg - Big Heads and Box Piramyd

at the final of the luxor level, on the big door go to the left, so you can enter on the sacred yards map. at one part of sacred yards you will need to press a big button to move the plataforms, go to the left and get the serious bag, it will run away so run and get it, after you get it, the walls will trap you and an adult mechanoid will explode the wall, kill it and move, now you are outside the map, go to the small entrance on the pyramid and you will see two big heads on an car with square wheels, go to the entrance and press the button, surprise!!!
An big pyramid made of serious boxes!