To cross a stream, street or valley (the place the hold off because of a flight of locks at possibly facet might be unacceptable) the valley is usually spanned by a navigable aqueduct – a famous case in point in Wales is the Pontcysyllte Aqueduct (now a UNESCO Globe https://riverqxdgj.bcbloggers.com/36188942/fascination-about-musica-infantil