Maybe the beginnings or cover for a missile silo. Surface feature look similar. Control rooms could be located at other locations that are built into the hillsides.
No, just spit-balling on the shape and appearance of the site. Also, missiles don't have to be nukes. Could be duds for FF, could be storage for explosives, could be a lot of things. The tennis court could just be an overlay on the image and not even exist.There is a bunch of what ifs that can be thought of. But, some of the structures built into hillsides lend themselves to underground structures that could be similar to that of missile emplacements.