To cross a stream, highway or valley (where by the hold off because of a flight of locks at either side will be unacceptable) the valley is usually spanned by a navigable aqueduct – a famed instance in Wales is the Pontcysyllte Aqueduct (now a UNESCO World Heritage Site) https://canalinfantil45443.prublogger.com/36193706/the-smart-trick-of-musica-infantil-that-no-one-is-discussing