This theory is furthered by the report of patriarch Dionysius I Telmaharoyo, who claimed that before al-Ma'mun's expedition, there already existed a breach in the pyramid's north face that extended into the structure 33 metres (108 ft) before hitting a dead end. This suggests that some sort of robber's tunnel predated al-Ma'mun, and that the caliph simply enlarged it and cleared it of debris.[138]

Descending Passage
From the original entrance, a passage descends through the masonry of the pyramid and then into the bedrock beneath it, ultimately leading to the Subterranean Chamber.
It has a slanted height of 4 Egyptian feet (1.20 m; 3.9 ft) and a width of 2 cubits (1.0 m; 3.4 ft). Its angle of 26°26'46" corresponds to a ratio of 1 to 2 (rise over run).[139]
After 28 metres (92 ft), the lower end of the Ascending Passage is reached; a square hole in the ceiling, which is blocked by granite stones and might have originally been concealed. To circumvent these hard stones, a short tunnel was excavated that meets the end of the Robbers' Tunnel. This was expanded over time and fitted with stairs.
