The Subterranean chamber - EARTH   

The Locality and its Gods

Subterranean chamber - earth
Queen's chamber - water
King's chamber - air
Sun's chamber - fire
Starry sky's chamber - aether

For the King or for the Priests?

Grand Gallery - fire on earth
To Gallery or water's chamber?
Interesting Ante-chamber
Earlier pyramids

The rock was meant to be here
It is a common assumption that the subterranean chamber was intended to be the King's burial chamber, but that it was given up during the building process. This should explain why the chamber never was "finished" and the builders never bothered to remove all the bedrock from it.
But if this is The Earth-god GEB's chamber (the only chamber cut directly out of the bedrock), what would be more appropriate than leaving some of the rock as a part of the chamber's equipment?

The Subterranean chamber is large, and it has a peculiar form with bedrock filling up in one end and having a deep hole in the other. The ceiling is square measuring about 8x14 meters (about 115 square meters!), longest in east-west direction. In the east end a deep square pit is cut out; it may have functioned as a well. The square form is turned 45 degrees compared to the pyramid's straight cardinal lines east-west and north-south.
The entrance to this chamber is in the eastern end of the northern wall. Almost directly opposite, just a little lower, a smaller corridor begins, but ends not long to the south.
The western end has a higher plateau made up from the bedrock that has been "left" in the chamber.
This was the Burial Chamber
A closer look at the form reveals that this most likely was the burial chamber of King Cheops.
It was the normal procedure to bury the body in a subterranean chamber and to have an adoration chamber on the ground.
There is a flat plateau on the rock big enough (2x5 meters) for a coffin or sarcophagus.
What has made it difficult for the egyptologists to accept this chamber as finished is simply the fact that the chamber looks unusual with all the rock in it.

Herodotus heard
The greek historian Herodotus visited Egypt round about 500 BC (circa 2000 years after Cheops). In his famous world history he wrote that he heard King Cheops was buried on an island in a large water-filled chamber under the pyramid, into which the water ran through a brick canal.
Actually he referred to what might very well be facts about Cheops's burial chamber.  

The island: the western part of the chamber rises above the eastern part in which one would arrive. The water: I think it was the egyptologist Perring who had the pit cleaned to a depth below the Nile surface (its height during ancient time's annual rise); he concluded it must have been a well, since any chamber lower than this regularly would be filled up with water. If we supply the well with a frame of wood (on two sides there is an edge/a shelf it can rest on) - we could tighten it with clay - we have a normal well from which we would be able to fill the lower part of the chamber with water. Filled to the right level it would look like the water was floating into the chamber from the square channel to the south. This would be the artificial water supply Herodotus told about. 

The writings of Herodotus has led to the assumption that there must be another hidden chamber in the ground below the pyramid. Others have thought that he must have been misinformed. But as you see he might have been right. The chamber still reveals how it may have been theatrically elaborated to remind the visitor of The Nile water flowing past the Giza plateau.

  to Queen's chamber - WATER...