There are three Grade I listed buildings in Rhondda Cynon Taf, a county borough in South Wales. In the United Kingdom, the term listed building refers to a building or other structure officially designated as being of special architectural, historical, or cultural significance. Listing was begun by a provision in the Town and Country Planning Act 1947. In Wales, authority for listing or delisting, under the Planning (Listed Buildings and Conservation Areas) Act 1990, rests with the Welsh ministers, though these decisions are based on the recommendations of Cadw. The Grade I buildings are a mid-18th-century bridge (pictured) in Pontypridd, and two structures related to the coal-mining heritage of the region: the engine house (1875) and the headframe (1902) of the Hetty Pit near Hopkinstown. The growth of iron foundries in Merthyr Tydfil led to the building of the Glamorganshire Canal (1791–1795) and the Taff Vale Railway (1841) to connect the industry to the docks at Cardiff; both of these passed through Pontypridd, contributing to its development into a major market town. (Full list...)