Gwynedd borders Anglesey across the Menai Strait to the north, Conwy, Denbighshire, and Powys to the east, Ceredigion over the Dyfi estuary to the south, and the Irish Sea to the west. The oldest city in Wales, Bangor is the largest settlement, and the administrative centre is castle town of Caernarfon. The preserved (ceremonial) county of Gwynedd includes the Isle of Anglesey. It has an approximate population of 117,400 people and has the highest percentage of Welsh speakers in Wales.