To cross a stream, street or valley (wherever the hold off attributable to a flight of locks at either side would be unacceptable) the valley is usually spanned by a navigable aqueduct – a famous case in point in Wales could be the Pontcysyllte Aqueduct (now a UNESCO Entire https://cesarqagld.bloggin-ads.com/60213423/not-known-facts-about-canal-infantil