We literally stumbled across this place by accident... I had done a bit of research on some psychiatric hospitals in the area but they were all a bust in terms of abandonment. While traveling through a town to get back on the highway we saw the patchy white facades of a large abandoned complex. The campus was a large square in the middle of town; a veritable green space surrounded by tall, spiked wrought iron fences topped with razor wire. These barricades were dotted with warning signs - we didn't need to know French to comprehend the picture of a slathering guard dog under the words "Terrain Militarie." There were no broken windows, graffiti, or any sign that people were getting inside.
The iron fence turned into chain link when it reached the highway where the property abutted on one side, and it looked like the most promising place to try. We stood in the tall reeds next to the highway, peering through the links, trying to listen past the roaring cars and gusts of wind. It was quiet in there; no barking dogs, no cars roaming the loop inside the rectangular arrangement of buildings... but we couldn't be sure what the situation really was in there from the few glimpses we had at the fence line.
We thought this out a little - here we were standing in a muddy hole in some random corner of France, where we may never get a chance to visit this place again; and so it was a mad dash to the nearest open window, dogs or no dogs.
The buildings were extremely empty - something I've come to notice about disused military installations in various countries over the years. The remnants of a hospital had been long gone, and it had looked like the buildings were last used as munition storage. However, some interesting signs and markings, together with the old architecture and wild wallpaper kept me interested.
There were no tunnels connecting the buildings, so we kept pushing our luck in sprinting from building to building, trying to get to the larger ones in the center without being seen by some guard that we may have dreamt up in our minds. We got midway across a large field and then stopped. The field was dotted with some tall grass and shrubs along our route that kept us hidden, but we reached a long parking lot and a road that was very open, and knelt down to assess the situation. I noticed deep paw prints in the sandy soil here, not yet eroded by a rainfall - it was time to leave, and fast. Try outrunning a guard dog and you'll know why!