[171]
To verify and pinpoint the void, a team from Kyushu University, Tohoku University, the University of Tokyo and the Chiba Institute of Technology planned to rescan the structure with a newly developed muon detector in 2020.[172] Their work was delayed by the COVID-19 pandemic.[173]

Antechamber
A diagram of the Antechamber
The last line of defense against intrusion was a small chamber designed to house portcullis blocking stones, called the Antechamber. It is cased almost entirely in granite and is situated between the upper end of the Grand Gallery and the King's Chamber. Three slots for portcullis stones line the east and west wall of the chamber. Each of them is topped with a semi-circular groove for a log, around which ropes could be spanned.
The granite portcullis stones were approximately 1 cubit (52.4 cm; 20.6 in) thick and were lowered into position by the aforementioned ropes which were tied through a series of four holes at the top of the blocks. A corresponding set of four vertical grooves are on the south wall of the chamber, recesses that make space for the ropes.

