Rectangular area with unknown function

 house, place with historical importance, abandoned / shut down

Photos:
1) web.archive.org/web/20161029131627/www.panoramio.com/photo/101679039 (recorded: 04.09.2013, published: 12.01. 2014)
2) web.archive.org/web/20161029131625/www.panoramio.com/photo/101679033 (recorded: 04.09.2013, published: 12.01.2014)
3) Hole with a wood-planking.Top of the picture: A top frame made ​​of wood. (recorded: 04.09.2013)
4) Not many camps have such a (still well visible) bearing moat (recorded: 04.09.2013)
5) Dry moat (recorded: 04.09.2013)
6) Hill, made by human hands (recorded: 04.09.2013)
7) Map with details

This rectangular area is bordering by a line of trees. The reason of that is, that there is a hydrologic difference in the ground. In the middle of the line is a water moat. Left and right of the moat, the ground is dryer then the moor near by. Trees can grow in this dry condition very well.
Inside the moat there are two lines of barbed wire fences. The first (in a distance of 6 m from the moat) was 4 m high the second (also in a distance from 6 m from the first fence) 2 m high.
Exact In the middle of this area is one block-hut, which is old, but in a good condition.
Near by (ca. 20 meter) is a hill (photo 6), made by human hands (5 x 5 m, 1 m high). On one side of this hill is a hole (photo 3). It may be, that it was a waterhole (spring) or a store.

But what was the function of the area???