The Lagan Canal near Belfast in Northern Ireland is typical of the massive canal construction of the 18th. century to link the new factories with their markets, ports, and sources of supply of fuel and raw materials. In this case the canal was used to carry coal and flax to the linen spinning and weaving mills, and to carry the finished product to the docks.
In the next century trains began to run along the valley with greater speed and carrying capacity than that of the horse-drawn barges. Many canals are being restored, now used for recreational and sometimes commercial traffic. The calm waters and the overgrown banks, with ready -made towpaths for walking on make canals attractive amenities.
Roads were carried over the canals on attractive 18th. century stone and brick viaducts. Sometimes the canals themselves were carried on aqueducts over roads and valleys.