Masurian Canal
Warmian-Masurian Voivodeship, Russia
The Masurian Canal (Kanał Mazurski, Masurischer Kanal) is a 50.4-kilometre-long (31.3 mi) abandoned canal in Poland and Russia in Central Europe. Planned to connect Königsberg (Kaliningrad) and Mauersee (Lake Mamry) in Prussia, construction of the canal was paused for the World Wars and hyperinflation in the Weimar Republic, before being abandoned.
Canal data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).