I've added a few more oddities to this collection.

In the far northwestern corner of the facility there is what may be the formal entrance to this facility complete with grand, decorative gateway. This would complement the security checkpoint at the 'back gate' in the far southeastern corner and define the limits of the facility.

Also at the entrance are two very tall towers, an array of smaller towers (windmills?), and the terminus of a 13 mile long covered trench. There are structures at each end of the trench and one almost exactly half way along its path.

Does the trench simply protect a water pipeline or secure channel communications to sensors at either ned of the trench? What could need covering that couldn't be run across the surface?

Interesting stuff.