To cross a stream, highway or valley (the place the delay caused by a flight of locks at either aspect might be unacceptable) the valley might be spanned by a navigable aqueduct – a well-known instance in Wales is definitely the Pontcysyllte Aqueduct (now a UNESCO World Heritage Web https://urso-fofo32109.eedblog.com/37302519/musica-infantil-an-overview