The Castlefield area has evolved bit by bit over a very long period of time. Innovations have proliferated here and artefacts have been constructed where they were needed. The Romans built their fort on elevated ground, partly protected by the rivers Irwell and Medlock. Canals were dug where natural water courses could be diverted to maintain water levels. Canal basins and wharves were so numerous by the time the railways were built that the only practical means of introducing railway transport was by building viaducts. The result is a multi-level environment which is unique in the world.
By 1850 there were distinct zones devoted to housing, warehouses and transport. Liverpool Road was an important highway, sloping gently down to the River Irwell, whilst the area occupied by the Roman road, connecting the fort with the north, had been re-developed for other uses. Deansgate now occupies the site of this road. At the east end of Liverpool Road the small-scale buildings on the south side are the residue of housing, most buildings having now been converted to commercial uses. Late 18th and 19th century housing to the north of Tonman Street has been replaced by modern housing.
Although the variety of building materials used in Castlefield is very wide, it tends to be more rugged and industrial in character than in other parts of the city centre. Stone, brick and slate are used extensively, but the most impressive building components are the massive cast-iron columns supporting the railway viaducts and, of course, the viaducts themselves, which are constructed of iron lattice beams. When the quays and canal branches were used for loading, unloading and transporting goods, they needed to be durable and resistant to the heavy pounding of horses' hooves and the iron rims of wagon wheels. Granite setts were therefore used as they were the most durable material available. After many years of use, the top surfaces became smooth and rounded.