Aerial view of Porthmadog. In 1811,William Madocks built a sea wall, known as the Cob, to reclaim a large proportion of the salt marsh for agricultural use. The diversion of the River Glaslyn scoured out a new natural harbour and as there was a deep enough draught, it could accommodate small ocean-going sail ships, so in 1825, the first public wharves were built. Slate from the Ffestiniog quaries were shipped from Porthmadog to all corners of the world and the town prospered. Photo taken 26 June 2005.