I stumbled upon this abandoned castle on the outskirts of Guell Colony in Spain. I was wandering around, with about 20 minutes of free time before I had to rejoin my group. I got to the edge of town and was surprised to see a tower poking up from behind a stand of trees. The hillside was clearly uncared-for, partly forested and crisscrossed with improvised trails. As I approached, I saw that it was not just a tower, but a small castle overlooking the river valley. It struck me as bizarre to see such an impressive building deserted and graffitied. The castle, to some extend, still serves the function of keeping intruders out. The gates were locked and I couldn't find a way to get in without climbing the walls. I would have liked to explore further, but my 20 minutes were up, and I had to go.
Someone had carved this hole in the wall, but it was too small to slip through.