To cross a stream, street or valley (where by the hold off brought on by a flight of locks at both side would be unacceptable) the valley may be spanned by a navigable aqueduct – a popular illustration in Wales could be the Pontcysyllte Aqueduct (now a UNESCO Earth https://urso-fofo67765.affiliatblogger.com/89230409/a-review-of-canal-infantil