Llys Rhosyr is just one of the llysoed, a kind of royal court, established by Llewelyn Fawr, a powerful 13th century Prince of Gwynedd. The remains of the palace were unearthed in 1992 by archaeologist Neil Johnstone. In the intervening years only about a quarter of the sizeable site has been excavated, leaving much still to be discovered.
The court at Llys Rhosyr was one of many such llysoed. The royal court was not established at one central location, rather, the princes travelled from one llys to the next on an irregular cycle, and each llys had to be prepared to receive the prince and his entourage.
Each llys was the focal point of a royal estate, called a Maerdref; in this case, Llys Rhosyr was the 'capital' of the Menai commote (district).
As far as we know, the site was abandoned around 1282, after the Edwardian invasion. Around 1330 a severe storm left much of the llys buried under sand. Excavations at Llys Rhosyr have yielded pottery, coins, and a number of other small artefacts.
Walls of three major buildings have been exposed, as well as the perimeter wall surrounding the site. The three buildings on view are thought to include the main hall of the llys, and a building beside it that was possibly the prince's private quarters.
Less than a kilometre from the site is the Pritchard Jones Institute in Newborough, where you can see an audio-visual presentation about Llys Rhosyr, which helps explain the importance of the site.