beyond the fence is a lot of whatever landscape is on the inside of the fence - if accessed through the forest, it would be forest land, if accessed through the foothills, it would be more of the same. wouldn't recommend trying to go through the swamp or lake areas though. about another 50 miles past the fence in the forest area would be a very old paved road in extreme disrepair - potholes, cracks, weeds growing everywhere, etc.

and yes, someone else could astral project through the door if it's held open for them!