Caldey Island width at its widest. It has an area of and its highest elevation is . The island lies in Carmarthen Bay on the northern side of the Bristol Channel in the county of Pembrokeshire, a little over south of Tenby on the mainland of southwest Wales. It is separated from the mainland by Caldey Sound. A ferry service from Tenby goes to Caldey Island in the spring and summer months when the weather allows. Boats depart every half hour from the harbour at high tide, while at low tide they depart from Castle Beach. Caldey Island consists of two islands
Pembroke and Tenby Railway on the South Wales Railway broad gauge main line but being on the narrow gaugelater known as standard gaugeit was not possible to run Pembroke and Tenby trains on the South Wales Railway lines to Carmarthen. The intention of the Pembroke and Tenby Railway was to make an alliance with other narrow gauge railways at Carmarthen, and the Great Western Railway (as successor to the South Wales Railway) did provide a narrow gauge link to Carmarthen. Experiencing financial difficulties, the company sold its line to the Great Western Railway in 1897. The South Wales Railway was incorporated in 1845 to