To cross a stream, street or valley (in which the delay caused by a flight of locks at possibly facet can be unacceptable) the valley could be spanned by a navigable aqueduct – a well-known example in Wales is definitely the Pontcysyllte Aqueduct (now a UNESCO Earth Heritage Internet https://eduardomvaeg.blogcudinti.com/37300837/a-review-of-canal-infantil