There are numerous river canals in Great Britain that form an intricate and extensive network. These structures have a long tradition in this country. It is thought that they started out as simple irrigation systems and, in the 18th and 19th centuries, during the Industrial Revolution, turned into means of transportation of merchandise. In some areas, however, some natural barriers had to be overtaken. For that, major engeneering work, such as tunnels and floodgates and, lately, some more ingenious solutions, had to be done.