To cross a stream, street or valley (wherever the delay due to a flight of locks at either facet can be unacceptable) the valley is usually spanned by a navigable aqueduct – a renowned instance in Wales would be the Pontcysyllte Aqueduct (now a UNESCO Entire world Heritage Internet https://canalinfantil18506.blogdosaga.com/37013184/what-does-canal-infantil-mean