To cross a stream, street or valley (in which the delay due to a flight of locks at both aspect will be unacceptable) the valley may be spanned by a navigable aqueduct – a renowned instance in Wales could be the Pontcysyllte Aqueduct (now a UNESCO Entire world Heritage https://energia-solar71592.activoblog.com/43082981/not-known-facts-about-canal-infantil