D-3271 is part of the Donau, a river that is located in Central and Eastern Europe. It is a major tributary of the Danube and it runs through countries like Austria, Slovakia, Hungary, Croatia, Bosnia and Herzegovina, Serbia, Montenegro, Bulgaria, Romania, and Moldova. It is the longest river in Austria and second longest in the whole of Europe. It is a great source of power and transport for the countries it runs through. Its waters are used for hydroelectric power, irrigation, and for recreational activities such as fishing, boating, and swimming.