|Name in D'ni||tiwa|
|Link-in point(s)||5 0 6 0 7 0|
The Great Shaft is the culmination of over two years' worth of work, performed primarily by the Guild of Surveyors, to dig a tunnel to connect the D'ni cavern to the surface of the Earth. Initially, such a construction was rejected because of the risk it posed to the security of D'ni, and so the Surveyors tunneled for over two years, at a maximum incline of 3825 torans (22.032 degrees). Eventually, however, the Guild Council grew impatient with the slow progress of the project, and so in 9336 DE they approved the construction of the Great Shaft, which bores straight up over three miles, stopping just below the surface.
Master Geran of the Guild of Surveyors designed the Shaft. It is a large cylindrical space with a single ramp threading its way down the side. At the top is an overlook balcony and a door leading to the last rest house before the surface. A similar rest house is located roughly halfway down the shaft.
At the base of the shaft, the ramp gives way to another observation deck. Flights of stairs dug into the rock behind the shaft wall connect this balcony to the floor. Four piers also extend out from the observation deck, but do not connect at the center, leaving an open-air space. The central portion of the shaft's floor is a platform which can be raised to connect the piers. The pillars supporting the piers act as massive screws, lifting and lowering the platform. Underneath is a service tunnel, which runs beneath the path leading out from the bottom of the Great Shaft. This tunnel provides access to the fan circulation controls in the adjoining node room.
According to the information on Aitrus' map, building the Great Shaft "required the four greatest rock-working machines in all of the D'ni Empire and a few months to complete." Unlike the small expedition team of surveyors who had managed the tunnel digging project on their own, the Great Shaft required a much larger team, with members from multiple guilds, from the Guild of Miners to the Guild of Caterers. Construction ran for several months, beginning in 9336 DE and ending in 9337.
When the shaft was nearly complete, an earthquake struck the area, cracking the wall and causing multiple injuries and fatalities. The incident nearly claimed the life of Veovis, a young D'ni Lord who had attended the dedication ceremony at the top of the shaft earlier that day. In the aftermath of the earthquake, the Council ordered that the shaft be repaired, and the entrance from the surface sealed. The decision to close the shaft was not a result of the earthquake, but rather a final reluctance on the part of the Council to permit contact with anyone who might live on the surface.
About 30 years after the Great Shaft was ordered sealed, a young woman named Anna and her father discovered the natural cave on the surface which led to the shaft's entrance. After the death of her father, Anna decided to explore the cave further. She found a small gap in the plug of stone which the D'ni had injected into the cave, and eventually navigated her way into D'ni itself. She was the only human to journey down the shaft before the fall of D'ni.
Centuries later, in the late 1980s, a man named John "Fighting Branch" Loftin rediscovered the Great Shaft, and over the next two decades, he—and later, the D'ni Restoration Council—would use the Great Shaft and the tunnels connected to it to access the underground cavern of D'ni. In 2003, Dr. Richard A. Watson returned to the surface by way of the Shaft following the presumed death of a DRC Restoration Engineer, Phil Henderson. On his way to the Surface, he stopped to rest in one of the rest houses located along the ascent, leaving his journal behind with a final note that he was going to take the Journey that Yeesha had been offering to explorers.
The Great Shaft also played a significant role in Myst V: End of Ages, which depicted the actions of Dr. Watson following his disappearance. Released by Cyan Worlds in 2005 and thought to have been created shortly after the events it depicts, the game shows a number of changes to the Great Shaft, including operating elevators, improved lighting, support struts to improve stability, and intermittent quakes. Dr. Watson's journal is gone, and the Nexus pedestals link to the rest Age of Direbo, rather than to the Nexus itself. Cyan, and RAWA specifically, have indicated that these changes were artistic in nature.
On April 25, 2007, a small portion of the Great Shaft was once again made accessible to explorers by the bahro, who placed a linking stone to Dr. Watson's rest house at the end of Tokotah Alley in Ae'gura. The shaft is currently in a state of disrepair. The service elevators are not running, and the ramp is too unsafe to use, especially in the dark. Explorers do not currently have access to either the base or the top of the shaft.