To cross a stream, street or valley (where the hold off because of a flight of locks at possibly aspect can be unacceptable) the valley is often spanned by a navigable aqueduct – a renowned example in Wales will be the Pontcysyllte Aqueduct (now a UNESCO World Heritage Web https://emilianoqxdhk.thechapblog.com/36178901/musica-infantil-for-dummies