These war remnants can be dangerous. When I was a teenager, I lived in the USSR, and once discovered a “zemlyanka” in a forest. This is basically a big hole in the ground with 2 beds shaped out of soil and a place for a small wood stove, it was then covered by trunks of trees as a roof, and covered with dirt, the entrance’s 3 steps downwards were covered with branches. It is close to invisible from the outside. They were used by “partizans”, the resistance people who attacked Germans from the forest. I was very proud of my discovery, and told about it to locals. They became highly alarmed and asked me if I went inside. I proudly said “Yes”. They told me that partizans frequently placed mines inside so when Germans came to investigate, it would blow up.