To cross a stream, highway or valley (wherever the hold off because of a flight of locks at possibly facet might be unacceptable) the valley might be spanned by a navigable aqueduct – a renowned illustration in Wales may be the Pontcysyllte Aqueduct (now a UNESCO World Heritage Web https://emilianolptwz.blogpayz.com/37281416/facts-about-urso-fofo-revealed