The shaft connecting the descending and ascending passage system in the Great Pyramid is called the Well Shaft.
It links the lower end of the Grand Gallery with the bottom of the Descending Passage, roughly 50 metres farther down. Unlike a simple straight tunnel, it follows a winding route through both the pyramid’s masonry and the natural limestone bedrock beneath it. Its upper section begins vertically, while its lower section descends through the bedrock at about 45 degrees.
The Well Shaft is also known as the Service Shaft or Vertical Shaft, which can cause confusion in quizzes and popular descriptions. “Air shaft” is a different label generally associated with the narrow ducts connected to the King’s and Queen’s Chambers. The Well Shaft is a passageway within the pyramid’s main circulation system, not one of those ducts.
Its original purpose remains uncertain. Proposed explanations include ventilation for the Subterranean Chamber and an escape route for workers who helped position the granite blocking stones in the Ascending Passage. A natural cave called the Grotto lies along its route.