The secret of the trees

I parked near that tree again today but with my back to it so I couldn't see it watching me - it turned out that was worse as I also couldn't see what it was up to. I soon stopped worrying about it though as I noticed I was surrounded by other trees, crowding around, unhappy with my presence. There was even one leaning around from behind that building so it could watch me. I began to suspect they were guarding something, some secret place that they shared....and then I looked at the building properly... what is going on in there? Is that some tree arched portal to another world or another time? It doesn't seem too welcoming...