One of the last explorations into the maps I drew in the Oak King three years ago and promptly forgot for all this time is this small fortification and the dungeons beneath.
Unlike most dungeons under a tower, these excavations have their own main entrance that is more easily accessed than the structure above. In fact, the way I pictured it was with a squad of unpleasant halfling assassins (grumpy about the lack of second assassinations after the first assassination of the morning… let’s not even get into the thought that there may not be an elevensies killing either) holed up in the structure and watching the lower dungeons from the doorway on the right side of the large dungeon chamber.
Of course, the party discovers this when they have to retrieve something from the lowest level of the dungeon, which involves either slipping past the halfling watch post, or very quietly “taking care” of the little blighters and then making the run downstairs and back up before the alarm is sounded.
Because, really, who wants to fight a dozen or so hungry halfling assassins?