Dock, town wall, and the Menai Strait

The map and aerial view show why Beaumaris was more than a free-standing stone fortress. Its dock was meant to let ships approach between the castle and town defenses, sheltered from weather and hostile fire unless an enemy already controlled those works. Keeping that route open required continual effort as land accumulated between the dock and the sea. The adjoining town grew faster than its planned wall, leaving only an incomplete defensive circuit around the settlement. At the larger strategic scale, Beaumaris and Caernarfon watched opposite ends of the Menai Strait and helped secure Anglesey against coastal threats from the north.