To cross a stream, highway or valley (wherever the hold off a result of a flight of locks at both side would be unacceptable) the valley is usually spanned by a navigable aqueduct – a well known illustration in Wales may be the Pontcysyllte Aqueduct (now a UNESCO Entire https://urso-fofo91100.boyblogguide.com/36051277/canal-infantil-an-overview