This first building is huge. You need at least a day to discover it completely, and even then it'll surprise you with another cellar or stairway you hadn't noticed.

I had my share of surprises when I bumped into four not so young vagabonds stealing tools and machinery. After the first moment of mutual distrust I convinced them I was not from the police and that I didn't care what they were doing as long as they didn't remove any ladders when I was upstairs !