Situated at the base of a hill is the ruins of a old castle. It's been there forever, but no one really goes there. I mean, it's all in shambles. However, there's a secret passage which leads to a very modern underground system. A few tunnels run all the way to buildings in the city, though most of not all of said tunnels need some refurbishing before they're fully functional. The base itself is well-lit and ventilated.