To cross a stream, highway or valley (where by the hold off because of a flight of locks at possibly aspect would be unacceptable) the valley is often spanned by a navigable aqueduct – a renowned case in point in Wales could be the Pontcysyllte Aqueduct (now a UNESCO https://kameronxwogy.arwebo.com/59494928/considerations-to-know-about-canal-infantil