Archaeological investigations were carried out at Poienari in the late 1960s, but they didn't disturb the existing walls and I'm not sure how extensive or rigorous they were by modern standards. There is a publication, but of course it's in Romanian (and not in Leeds library anyway) and without being able to read that directly I've struggled to pin down any very reliable information about it. I know that the square watch-tower definitely pre-dates the rest of the structure, but there seems to be some debate as to how much - some say it's as early as 1200, some as late as the 1410s.