>>7102638The only real underground exploration I did was in an old brewery complex right here in my city (which sadly got demolished two years ago).
There were at least three huge sprawling levels down and several levels up with most of the equipment still in place. The lowest level had huge tanks connected with ladders and metal walkways.
I don't have any pictures from there because it wasn't that impressive to look at, but the feeling of exploration was actually one of the most memorable so far because it was such a maze to get lost in.
