Pefect place to visit Vienna, right in the centre, opposite to the Otto Wagner House, sixth floor, overlooking the Graben and nice views on the former Otto Wagner atelier (and later Hundertwasser atelier) as well as other well known buildings. Cafe Europa, on the ground floor of the building, is a relaxing coffee shop with friendly staff and open early till late.
Caroline is an excellent host who made me feel welcome from the start. Overall, a highly recommendable place for a Vienna visit.