Access Lift
General Information
The Access Lift is the first facility you get to place in every new base, with the exception of the default base. Its construction is instantaneous so you can start building four new facilities off it right away.
The Access Lift is also one of the two entry points aliens can take to get into the base.
The Access Lift is literally impossible to destroy, so it's safe to shell the Access Lift with as many explosives as you wish in order to defend it from any invaders.
Dismantling a Base
To fully dismantle a base, you must first remove everything, from equipment, to vehicles, to staff and to base modules. Until the Access Lift is on its own, the base cannot be dismantled.
If you only have one base left, you can indeed dismantle it down to the Access Lift and remove the base of the map. Don't worry, you won't lose the game. As long as you have enough money, you can relocate elsewhere and start afresh.