To cross a stream, highway or valley (where the hold off attributable to a flight of locks at both facet could well be unacceptable) the valley is often spanned by a navigable aqueduct – a well-known example in Wales could be the Pontcysyllte Aqueduct (now a UNESCO Entire world https://charlieemuzh.yomoblog.com/43950465/the-definitive-guide-to-canal-infantil