To cross a stream, street or valley (wherever the delay caused by a flight of locks at possibly facet could well be unacceptable) the valley is usually spanned by a navigable aqueduct – a famed instance in Wales could be the Pontcysyllte Aqueduct (now a UNESCO Earth Heritage Web https://comprarinstagramviewsreel39886.blogsidea.com/43664747/canal-infantil-fundamentals-explained