What is it?

I just don't know. This strange construction seems to be made entirely of cement and is being erected inside a nature preserve in Busca Vida. This picture just doesn't do it justice. It seems to be a boxcar in the style of Frank-Loyd-Wright-meets-Salvador-Dali-kind-of-esk. There do no seem to be any roads to it and we didn't see any movement indicating an inhabitant. I have no idea what it's doing there, since I thought no one was allowed to build on or walk around in these federal preserves....