This would be their finest achievement, the castle to end all castles. The end result was a massive fortification with near-perfect symmetry. There are four concentric rings of powerful defenses, including a water-filled moat complete with its own pier. The original entrance was through an advanced system of portcullises and bars. These were so effective that the castle did not need a large garrison; only 20 men were assigned to guard it. The great hall could accommodate up to 300 people. It had a domed roof made of copper covered in gold leaf. Paintings by Dutch artists Rubens and Van Dyck decorated the walls. Other luxury items for sale in the market square included jewelry, clothes, and weapons. Beaumaris was built between 1540 and 1565 by Sir Hugh Owen, the owner of several manors in north Wales. The castle was intended to protect against attacks from England's rival power, France. It is said that its creator wanted it to be the best-defended castle in all of Wales but also one that would be attractive to visitors, so he divided it into three sections with four towers each. He also placed the main entrance on the south side of the building where there was no view of the sea. Although the castle was never attacked, it did serve as a prison for many years after its construction.