When my flight to Malta and its 3 WHS was canceled because of the volcano, I made a nice train trip instead to St. Gall in Switzerland. It is a medium-sized town with a very pleasant centre full of historic buildings and half-timbered houses. The religious complex in the immediate city centre, consisting of the cathedral and the convent, is a World Heritage Site. Both buildings have a medieval (Carolingian) origin, but were heavily rebuilt in Baroque style. Both are quite nice, but the unmissable part is the library. You can actually only visit one room, but it is full of books and manuscripts that are up to 1,200 years old. A must-see for any history buff.