Cardiff in making iron and later steel, brought to the sea by packhorse from Merthyr Tydfil. This was first achieved by the construction of a long canal from Merthyr (510 feet above sea-level) to the Taff Estuary at Cardiff. Eventually the Taff Vale Railway replaced the canal barges and massive marshalling yards sprang up as new docks were developed in Cardiff – all prompted by the soaring worldwide demand for coal from the South Wales valleys. At its peak, Cardiff's port area, known as Tiger Bay, became the busiest port in the world and – for some time – the world's
Cardiff Bay Barrage Penarth, cutting two miles off the journey otherwise taken on the heavy-traffic roads further upstream. However, this benefit took years to materialise due to a lack of agreement between the derelict access land owners (Associated British Ports) and Cardiff Council. The "unfinished" barrage was the cause of much embarrassment to the Welsh Assembly. Cardiff Harbour Authority made significant progress in the creation of the bay edge walkway and have redeveloped a large portion of the previously inaccessible bay periphery and the bay edge walkway was finally completed and open to the public on Monday 30 June 2008, allowing public access