section_path: Interior/Grand Gallery
section_name: Grand Gallery
paragraph_text: Grand Gallery
  
  The Grand Gallery continues the slope of the Ascending Passage towards the King's Chamber, extending from the 23rd to the 48th course (of stones), a rise of 21 metres (69 ft). It has been praised as a "truly spectacular example of stonemasonry". It is 8.6 metres (28 ft) high and 46.68 metres (153.1 ft) long. Its walls are made out of polished limestone. The base is 4 cubits (2.1 m; 6.9 ft) wide, but after two courses – at a height of 2.29 metres (7.5 ft) – the blocks of stone in the walls are corbelled inwards by 6–10 centimetres (2.4–3.9 in) on each side.
  
  There are seven of these steps, so, at the top, the Grand Gallery is only 2 cubits (1.0 m; 3.4 ft) wide. It is roofed by slabs of stone laid at a slightly steeper angle than the floor so that each stone fits into a slot cut into the top of the gallery, like the teeth of a ratchet. The purpose was to have each block supported by the wall of the Gallery, rather than resting on the block beneath it, in order to prevent cumulative pressure.
  
  At the upper end of the Gallery, on the eastern wall, is a hole near the roof that opens into a short tunnel by which access can be gained to the lowest of the relieving chambers.
  
  The floor of the Grand Gallery has a shelf or step on either side, 1 cubit (52.4 cm; 20.6 in) wide, leaving a lower ramp 2 cubits (1.0 m; 3.4 ft) wide between them. There are 56 slots on the shelves, with 28 on each side. On each wall, 25 niches have been cut above the slots. The purpose of these slots is not known, but the central gutter in the floor of the Gallery, which is the same width as the Ascending Passage, has led to speculation that the blocking stones were stored in the Grand Gallery and the slots held wooden beams to restrain them from sliding down the passage. Jean-Pierre Houdin theorized that they held a timber frame that was used in combination with a trolley to pull the heavy granite blocks up the pyramid.
  
  At the top of the gallery, there is a step onto a small horizontal platform where a tunnel leads through the Antechamber, once blocked by portcullis stones, into the King's Chamber.