The archaeological site of Llys Rhosyr is easily missed by motorists on their way to Llandwyn Island. It is located at a bend in the road, just past the church. Here, archaeologists have uncovered the foundations of a medieval court in use before King Edward I invaded Wales. It was one of several small courts on Anglesey where Welsh princes stayed while collecting rents and holding law courts. The masonry is several feet high in places. An audio-visual show about the Royal Court can be seen at the Prichard Jones Institute in Newborough.