God of War Easter Egg - Original Artworks in the Tomb!

1) Play the game until you'll be in a level called The Architect's tomb.

2) Go through the level. Nearly at the end, you'll be in the architect's studio, where he and his wife are buried.

3) Explore the tomb and press R2 near the walls on the next and on the right. You will see the architect's plans for the Temple.
Actually, they are original concept artworks drawn by the creators of the game.
You also can see their signatures on the last one.