A small coastal town (population 4,200), it developed in the C19th as a port exporting slate. It came into existence after a sea wall (The Cob) was built in 1811 to reclaim land from the sea for agricultural use and the diversion of the river formed a new natural harbour.
The Ffestiniog Railway's station is located at one end of The Cob and its historic trains can take you on a 13.5 mile journey to Blaenau Ffestiniog as they climb over 700 feet from sea level into the welsh mountains.
To the north of Porthmadog is the picturesque village of Beddgelert. The Welsh Highland Railway has been restored with narrow gauge steam trains running to Caernarfon and Porthmadog.
The Glaslyn Osprey viewing centre is near Porthmadog and from when the ospreys return from West Africa (usually end of March) until August, visitors are able to watch the family via live nest cam images.
Sygun Copper Mine is situated NE of Beddgelert; it was abandoned in 1903 but now self-guided audiovisual tours allow visitors to explore the old workings on foot. There are winding tunnels and large colourful chambers, magnificent stalactite and stalagmite formations and copper ore veins which contain traces of gold, silver and other sought-after precious metals.