To cross a stream, road or valley (exactly where the delay a result of a flight of locks at both aspect can be unacceptable) the valley might be spanned by a navigable aqueduct – a popular illustration in Wales is definitely the Pontcysyllte Aqueduct (now a UNESCO World Heritage https://urso-fofo90000.canariblogs.com/urso-fofo-things-to-know-before-you-buy-51955756