To cross a stream, highway or valley (where by the hold off because of a flight of locks at possibly aspect could well be unacceptable) the valley may be spanned by a navigable aqueduct – a popular instance in Wales may be the Pontcysyllte Aqueduct (now a UNESCO Globe https://gregoryjopnj.blue-blogs.com/44758554/5-easy-facts-about-musica-infantil-described