I bicycled 850 miles (1350 km) from the source of the Danube River in southwestern Germany to Budapest, Hungary. It is a great trail that is almost entirely separate from roads. It is flat with few hills since it follows the Danube River. It passes through many villages, so there are plenty of places to sleep and eat and get water along the way. The section between Passau and Vienna is particularly popular and busy. The beginning from Donaushingen to Passau is nice and well-maintained but less trafficked. The part from Vienna to Budapest is nice, although it gets a bit rougher and less well marked in Hungary. The trail continues following the Danube River to the Black Sea. I stopped at Budapest.