The Elevator is an elevator between the Mansion and the Basement. Whether the Elevator also has access to the upper floors is unknown. What levels it can open up to is unknown. Currently, we do know that it opens up to Leny Hall.
What is most significant is that it houses and imprisons the Operator. For this reason, the elevator cage is made form cold-forged iron.
It is also implied that the Operator has access to the Mansion's systems through the Elevator. Which again raises the question about sanity and why use the Operator as an elevator-operator, thus creating this security-hole.