To cross a stream, road or valley (where by the delay a result of a flight of locks at both facet would be unacceptable) the valley may be spanned by a navigable aqueduct – a famed instance in Wales could be the Pontcysyllte Aqueduct (now a UNESCO Planet Heritage https://connercjnqu.popup-blog.com/36051176/not-known-facts-about-canal-infantil