Castillon has two large elevators linking the lower galleries with the medium level. As you can see on the previous photo the work Castillon was built in a small mountain. This posed two problems for the designers. Firstly it seriously limited the space for the different underground rooms. Secondly the shafts to the blocks had to be very high. This was solved by building two levels of galleries. The lower level held the barracks, the power plant and the entrance of the work. The second level gave access to the different blocks.