Taken from touregypt:
Another very recent (1991) and important find by Dr. Hawass was the cult pyramid, discovered under a mound of sand during cleanup work and now designated G 1d. This is a tiny structure about 25.5 meters southeast of the corner of Khufu's pyramid, covering an area of approximately 24 square meters. The remains include fine, Tura quality limestone blocks from the pyramids outer casing and perimeter foundation, some of which remain in situ, large blocks of cruder limestone and debris that filled the core of the pyramid, and a T shaped substructure. The original baseline, marking the foot of the lowest course of casing blocks, is preserved on five foundation slabs on the east side and seven on the south side. No remains of the original baseline was found on the north side, where most of the foundation slaps were missing. On the west side, there is only one foundation block in situ that carried the baseline. However, an estimate was made of the base length of a site at 21.74 meters. The average slope of the preserved faces is A view of the cult pyramid (foreground) at the Pyramid of Khufu at Giza52.4 degrees.
Also discovered was the cult pyramid's pyramidion, the pyramid shaped stone that caps its top. It is a single piece of fine limestone, and is the second oldest pyramidion ever found.
The substructure of the cult pyramid consists of a sloping entrance passage about one meter wide originating from the north side of the structure, which lead down for 5.35 meters to a rectangular chamber oriented east west and measuring about eight meters by three and a half meters. There is a cutting in the floor of the rectangular chamber about one meter wide, immediately in front of its entrance from the descending corridor. The walls of the chamber stand 2.85 meters high, and slope slightly inward as they go up.
At the west end of the chamber there are four small holes, a pair on each of the north and south walls. They appear to be sockets for wood cross beams, perhaps used to lower or cover an object in the west end of the chamber.
The cult pyramid has been partially restored. Some of the fallen blocks and restored parts of the structure were replaced with new masonry. The apex of the pyramid, incorporating the pyramidion and the trapezoidal block from the third course down has been reconstructed using new blocks.
His discovery put an end both to doubts that such a cult pyramid existed in the Khufu complex, and to speculations about its identification with the so-called test passageway. The "test passageways" were corridors cut into the underlying rock that imitated on a smaller scale (about 1:5) part of the Great Pyramid's substructure, consisting of the descending and ascending corridors, the lower part of the Great Gallery, and even by implication the horizontal passageway that leads to the Queen's Chamber. Scholars suggested that this was a model used by the builders of the Great Pyramid to test their methods of blocking passageways but some had associated it with a cult structure.