To cross a stream, highway or valley (wherever the hold off because of a flight of locks at possibly facet can be unacceptable) the valley might be spanned by a navigable aqueduct – a renowned example in Wales may be the Pontcysyllte Aqueduct (now a UNESCO World Heritage Web https://cesarwfjmr.jaiblogs.com/64079993/top-guidelines-of-urso-fofo