Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Pencader Tunnel is an abandoned railway tunnel on the old trackbed of the Carmarthen to Aberystwyth main line in south-west Wales. It was originally bored for the Llanpumsaint-Pencader section of the Carmarthen & Cardigan (C&C) Railway. It is approximately 895 yards (818 m) long (just over half-a-mile), making it the longest tunnel in West Wales and is bored through Ordovician shales. It is single-track and built to the C&C's adopted broad gauge dimensions, as opposed to the smaller standard gauge used on Britain's railways today. It is also known as alternatively Alltwalis Tunnel and Dolgran Tunnel to local villagers.