Beaumaris Castle, located in Anglesey, Wales, was built as part of Edward I's conquest of North Wales in the late 13th century. Despite being considered one of Britain's most symmetrical castles, it was never fully completed due to funding issues and interruptions from wars. Over the centuries, the castle fell into disrepair, with leaks and inadequate defenses, but it still stands today as a popular tourist attraction, showcasing impressive medieval military architecture.