Horrenberg lies on a road between Speyer, Bad Wimpfen, and Nuremberg that has been in use since Roman times. This road, named an imperial highway ("Reichstrasse") in 1433, was one of the most important thoroughfares in Germany up until the late Middle Ages. In medieval documents, the road is often referred to as the "Kaiserstraße", the emperor's highway, because over the centuries many high ranking personalities used the imperial highway. The Roman general Julian (359), the king of the Huns Attila (451), king Conrad III (1150), king Philipp of Swabia (1199), emperor Frederick II (1205), and king Henry VII (1224) all sojourned past the place where Horrenberg stands today. A valuable glass fragment from the 11th or 12th century found at castle Horrenberg indicates the passing of royal parties. This kind of purple-red and white glass has otherwise only been found at St. Denis in Paris, in Italian Pavia, and in Birka near Stockholm.