The Great Lift at Mzinchaleft is an ancient Dwemer mechanical lift that connects to Blackreach. The iron gate will initially be locked, and can only be opened from the inside. This can be achieved once the Dragonborn has access to Blackreach (the only way to do this is to have started the quest, Discerning the Transmundane as Septimus Signus’ Attunement Sphere is required to open a door to Blackreach). From Blackreach, the Dragonborn can ride the Great Lift at Mzinchaleft up to the surface and pull a lever to open the gate, after which the lift can be entered from the outside anytime it is traveled to and will appear on the world map separate from Mzinchaleft.
360 PC Especially prone to "locking up", trapping the Dragonborn in a repeating cycle of arriving at either the surface or Blackreach. This overwrites all the autosaves, so it is a good idea to save before activating this lift.
Pressing all the buttons and then clicking on the Xbox button and leaving the menu open may break the cycle.
Repeatedly pressing the Favourites button may break the cycle.
Disabling auto-saves may break the cycle.
360 When leaving Blackreach via this lift, the Dragonborn may appear in the overworld several meters ahead of where he should, outside of the elevator cage. If this was the first time the location was used, this will mean that the door to the elevator cage will still be closed with the switch on the other side, rendering this particular lift useless as a return point until it can be access from Blackreach again.
The gate may close itself at any point after being opened and returned to. When this happens, the other gates will close as well and enemies in the ruins and blackreach will respawn.
It is possible to circumvent this problem and still get into Blackreach. By standing against the gate of one of the above-ground lifts and casting Summon Arvak, it is possible to get through the gate by mounting and then unmounting Arvak. You can then use the lever to open the gate and descend into Blackreach. Note: If it worked correctly, Arvak will appear to be halfway through the gate.
Another way to circumvent this is by standing at the gate and holding a plate in front of you and running into it. You must move the plate around to find the correct spots that allow you to move through the gate.