Danube-Auen National Park on both land and water, and other invertebrates, the total number of species in Donau-Auen National Park is estimated to be at least 5,000. Danube-Auen National Park Donau-Auen National Park () covers 93 square kilometres in Vienna and Lower Austria and is one of the largest remaining floodplains of the Danube in Middle Europe. The German word Aue (variant Au) means "river island, wetland, floodplain, riparian woodland", i.e. a cultivated landscape in a riparian zone. The words Aue and Au occur in a large number of German place names—including Donau, the German word for the Danube River—and refer to forests,
Danube Drava, Sava and Tisa. In Serbia, a canal network also connects to the river; the network, known as the Danube–Tisa–Danube Canals, links sections downstream. In the Austrian and German sections of the Danube, a type of flat-bottomed boat called a Zille was developed for use along the river. Zillen are still used today for fishing, ferrying, and other transport of goods and people in this area. The importance of fishing on the Danube, which was critical in the Middle Ages, has declined dramatically. Some fishermen are still active at certain points on the river, and the Danube Delta still has