Rotterdam acquired a metro line in 1968, the first Dutch city to do so. Six kilometres long to begin with, this north-south line ran from Central Station to Zuidplein. Once south of the Maas, the metro emerged from below ground level. There was enough room here for a viaduct, which was cheaper and more quickly built. Consisting of precast elements - 33 metre long prestressed beams, tapering columns and a cladding of ornamental concrete panels - this viaduct is the most visually definitive feature of the metro together with the metro stations Maashaven and Rijnhaven. These stations may not count for much in architectural circles, yet with their strapping concrete structures they mesh wonderfully well with the large-scale rational architecture of the Rotterdam docks.