 The TVR line would dominate the transportation of coal throughout the Rhondda 's industrial history , and its monopoly was a point of contention , as with no rivals the colliery owners could not negotiate for haulage rates . Several attempts were made to break the monopoly including the opening of the Rhondda and Swansea Bay Railway , between 1885 and 1895 , which linked Blaenrhondda at the head of the Rhondda Fawr to the Prince of Wales Dock . To achieve this rail link the Rhondda Tunnel was constructed through Mynydd <unk> to <unk> ; at the time the longest railway tunnel in Wales . 
