The Grand Gallery is actually a pulley to move the massive granite slabs into place.
https://www.dailymail.co.uk/news/article-6524855/Canada-PM-Justin-Trudeau-surprise-visit-forces-Mali.html
https://thehill.com/policy/national-security/422659-schiff-democrats-will-subpoena-mueller-report-if-trump-tries-to-hide
Schiff: Democrats will subpoena Mueller report if Trump tries to hide it