To cross a stream, street or valley (in which the delay due to a flight of locks at possibly facet might be unacceptable) the valley might be spanned by a navigable aqueduct – a popular instance in Wales may be the Pontcysyllte Aqueduct (now a UNESCO Globe Heritage Web https://musica-infantil13277.total-blog.com/the-ultimate-guide-to-urso-fofo-62416125