To cross a stream, street or valley (the place the hold off because of a flight of locks at possibly facet can be unacceptable) the valley might be spanned by a navigable aqueduct – a famed case in point in Wales could be the Pontcysyllte Aqueduct (now a UNESCO https://urso-fofo56654.full-design.com/canal-infantil-for-dummies-79504549