more a palace than a castle, but anyway. Australia, but moved to Singapore when I was about six, and lived there for five years, hardly ideal /out/ing territory. but opposite our apartment block there was this big stretch of jungle, so thick you couldn't see more than 2 metres or so in from outside. at the front was this big old fashioned mansion, which apparently was briefly used by the Japanese general during the ww2 occupation. supposedly he used to take prisoners there to torture/kill them, so a lot of the locals thought that it was haunted, and the place was left abandoned (Singapore has crazy high real estate prices, and a population of 6 million on a tiny island, so abandoned acreage mansions just aren't a thing). as kids, we naturally bought into the idea of having a haunted house opposite us, and it was probably another two or three years before we actually went inside, but when we did it was great.
meanwhile, behind the mansion was this big ass untouched jungle, right in the middle of the inner suburbs. when I was about the same age, me, my brother and my dad put on full larpy /out/ gear and went in to explore it. my dad had done some research and knew what was inside, but I had no clue. the jungle was thick enough that you couldn't just walk in a straight line along the ground, we had to constantly climb over branches, or through trees in order to move forward. it probably took about twenty minutes, but eventually we stumbled across this huge idiana-jonesesque mansion in the middle of the forest. pic related, but the photo's quite old, when we found it the roof had mostly caved in, and the jungle had partly reclaimed it, but you could still tell it for what it was.