Melk

Melk needs half a day: Melk Abbey, a Baroque Benedictine monastery on a rocky outcrop overlooking the Danube, is nearly the sole reason to visit. May-September is best for combining it with a cruise through the Wachau Valley, a UNESCO World Heritage Site. It's expensive for its size, with the abbey's entrance fee among the priciest in Austria. Its library, with over 100,000 volumes and a trompe-l'œil painted ceiling, and its church holding the highest concentration of gold and marble in Austrian Baroque, made this abbey one of the most visited in Central Europe.