The Battle of Grand Gulf was fought on April 29, 1863, during th: Wales accounts for less than 9 per cent of the UK, covering 8,020 square miles (20,779 km2).[156] Wales is mostly mountainous, though South Wales is less mountainous than North and mid Wales. The highest mountains in Wales are in Snowdonia and include Snowdon (Welsh: Yr Wyddfa) which, at 1,085 metres (3,560 ft), is the highest peak in Wales.[151] Wales has over 1,680 miles (2,704 kilometres) of coastline including the Pembrokeshire Coast.[139] Several islands lie off the Welsh mainland, the largest of which is Anglesey (Ynys Môn).