To cross a stream, highway or valley (in which the delay brought on by a flight of locks at possibly facet might be unacceptable) the valley might be spanned by a navigable aqueduct – a renowned illustration in Wales may be the Pontcysyllte Aqueduct (now a UNESCO Globe Heritage https://simonlswyc.blogrenanda.com/43691262/a-secret-weapon-for-musica-infantil