To cross a stream, road or valley (where by the delay because of a flight of locks at either facet could be unacceptable) the valley is often spanned by a navigable aqueduct – a well-known instance in Wales will be the Pontcysyllte Aqueduct (now a UNESCO Earth Heritage Website) https://cesarqagld.bloggin-ads.com/60213423/not-known-facts-about-canal-infantil