"The Wachau is a stretch of the Danube Valley between Melk and Krems, a landscape of high visual quality. It preserves in an intact and visible form many traces - in terms of architecture, (monasteries, castles, ruins), urban design, (towns and villages), and agricultural use, principally for the cultivation of vines - of its evolution since prehistoric times."
That is the introduction on the UNESCO world heritage web page. Much more is not necessary to write, it is just a pretty area with good food, lots of white wine and many interesting monuments and villages.