Imhotep designed the Step Pyramid of Djoser to serve as a gigantic stairway by which the soul of the deceased pharaoh could ascend to the heavens. Such was the importance of Imhotep's achievement that he was deified by later Egyptians.
Before you can ascend to the top of this pyramid level, you must make your way to the bottom. To get the top piece of treasure, move left off the apex, dig the next block and step onto the mummy below, continuing to move right (try placing your mouse pointer on the apex).
After getting the last piece of treasure, exit to the right and run up and down the ladders. The lower left is the only difficult part: just run under the mummies on the ladder above you and maneuver ... and hope!