By building the Base in an old mine, the engineers were able to create a maze of hundreds of kilometers. The drilling of the Base's network tunnel still continues today (but at a slower pace), in order to create new laboratories with greater capacity. As explained in the Inside Base
image, it is really difficult to estimate the duration of such construction : Some years 3km of new tunnels are built, while the other years they are renovated and modernized.
The example of the tunnels of the oil complex of Jurong Island Rock Caverns
gives a small idea of the magnitude of the task.
Typically, the entrance to the "maze" is only protected by a single door, but other doors can be closed if the route of certain vehicles must be secured.
The checkpoint on the right corner perform biometric analysis of physical characteristics of individuals : It compares the visitors to a recent 3D model of them. For visitors in which the Base can't be absolutely certain of, that control is the first of a very long list. Such a checkpoint makes it difficult to introduce computer viruses in the network of the Base, because during this identity check, the visitor doesn't have any contact with an electronic device.
If the door opens, the system will guide the visitor through the maze (and if it doesn't, that's a bad omen). Different types of sensors are positioned every 10 meters to continuously track them, and their route will be transmitted by "Li-Fi lamps" positioned every 5 meters. Without this guidance, it's almost impossible for newcomers to locate inside the tunnels.
Those suspected of being spies, will be automatically redirected to some places where they will undergo further checks (their path won't go directly to the center of the Base). After these reviews and inspections, a train will transfer them to the center of the Base : This road being the most protected, it is not with this method that an enemy will infiltrate the Base.
The most sensitive areas are only accessible by train :
Everyone knows that the hackers who work in the "towers" can't get out without taking the train. In general, those who work in these areas will experience a "preventive isolation", though it's not forever : All they have to do is ask to join the "Center" of the Base.
Art by www.steevenlabeau.net