Five places where engineers refused to let a river interrupt a canal and simply carried the canal over it — boats and all — in a trough of iron, steel or concrete high above the water below.
Thomas Telford and William Jessop's Pontcysyllte Aqueduct (1805) carries the Llangollen Canal 38 m above the River Dee; UNESCO inscribed it in 2009. The International Musical Eisteddfod has run since 1947.
The Pont-canal de Briare (1890–96) carries the Canal latéral à la Loire 662 m across the Loire; its piers were by the Eiffel company. It was the world's longest navigable aqueduct until Magdeburg's opened in 2003.
Nils Ericson's iron aqueduct on the Dalsland Canal opened in 1868, held together with some 33,000 rivets; road and rail bridges were later built above it. The canal runs mostly through natural lakes.
The Mittelland Canal crosses the Weser on the 1914 Minden Aqueduct, with a second trough added in 1998. The Battle of Minden was fought on 1 August 1759; the Porta Westfalica gap lies 5 km south.
The Magdeburg Water Bridge (2003) carries the Mittelland Canal 918 m over the Elbe to the Elbe-Havel Canal, the world's longest navigable aqueduct. Otto von Guericke demonstrated his hemispheres in 1654.
Think you'd have found them? Play today's expedition, or replay this one from the archive.