This is a beautifully-rendered plan of an old gaol, a simple hexagonal walled courtyard with a grate over whatever horrors you decide are to be found below! The cover illustration and 360° view show a guard tower, barred openings and a walkway for warders to patrol, plus an open field around with a path leading up to the front gate.
The accompanying notes suggest that maybe the place was abandoned after some dread creature got loose in the dungeons beneath, the last guards to flee fastening the grate securely. Pity the convicts left trapped below... and pity those who to this day hear their shades wailing. Brave adventurers may be tasked with allowing the dead finally to rest in peace.
Or maybe it's still in use. I don't know about your players, but some of mine need locking up! This might be a suitable facility... or maybe some evil overlord uses it and the characters want to rescue someone.
Plenty of scope for what on the surface seems to be a simple old gaol. Enjoy...