The Wachau is an Austrian valley with a picturesque landscape formed by the Danube river. It is one of the most prominent tourist destinations of Lower Austria, located midway between the towns of Melk and Krems that also attracts "connoisseurs and epicureans" for its high-quality wines. It is 36 kilometres in length and was already settled in prehistoric times. A well-known place and tourist attraction is Dürnstein, where King Richard I of England was held captive by Leopold V, Duke of Austria. The architectural elegance of its ancient monasteries , castles and ruins combined with the urban architecture of its towns and villages, and the cultivation of vines as an important agricultural produce are the dominant features of the valley.