To cross a stream, road or valley (in which the delay attributable to a flight of locks at both aspect could be unacceptable) the valley might be spanned by a navigable aqueduct – a well-known example in Wales is the Pontcysyllte Aqueduct (now a UNESCO Environment Heritage Site) through https://elliottqafim.blogstival.com/58685340/indicators-on-canal-infantil-you-should-know