Reclaimed a worldgen fort, and saw a few corpses on the top level. I immediately got "an ambush! Drive them out!" spotting some dwarves and goblin nobility at the depot. I sent my dwarves downstairs and found a total population of about ~60 dwarves, 5 humans, and a dozen goblins (all the goblins are nobles). Marked as "hostile" on the unit list, but none of them reacted to my dwarven squad until I put in a kill command.

Related to bug report 6600

Also, there's an "unusable downward slope" out in the middle of open air in the caverns (caused by a towercap?), looks like it's related to bug 7441.