To cross a stream, highway or valley (wherever the hold off due to a flight of locks at either facet could be unacceptable) the valley might be spanned by a navigable aqueduct – a famed example in Wales is definitely the Pontcysyllte Aqueduct (now a UNESCO Globe Heritage Web https://ursofofo89987.humor-blog.com/35883394/helping-the-others-realize-the-advantages-of-musica-infantil