The Great Pyramid Shafts

The shafts that extend from the northern and southern walls of the Queen's chamber have been found to have doors with copper bolts inside them. Perhaps behind one of these doors we will find a sarcophagus containing the missing mummy of Khufu's mother, Hetepheres, and the shaft will turn out to be a symbolic corridor leading to her burial chamber.

We know Khufu's sarcophagus had to be placed in the King's chamber at the time of that chamber's construction. The same may be true for his mother, who may be in a chamber just big enough to hold a sarcophagus within the masonry of the pyramid.