Schematic section of the Great Pyramid. (Note that these are the known voids and chambers—more have since been identified by muon scanning, the nature of which is unknown.) 1. Original entrance. 2. New entrance (“tourist” entrance, a forced tunnel by the ninth-century Caliph Al-Ma’mun). 3. Descending corridor. 4. Descending tunnel. 5. Lower chamber. 6. Ascending corridor. 7. Intermediate chamber (or “of the Queen”) and relative ventilation ducts. 8. Horizontal corridor. 9. Great Gallery. 10. Upper chamber (or “of the King”) and relative ventilation ducts. 11. Vertical tunnel.