Charlemagne had Aachen built up into his favorite residence. From here he ruled over his huge empire, which stretched from the North Sea to the Mediterranean. To improve understanding in his multi-ethnic empire Charlemagne standardized the system of writing by introducing lower case letters. He himself couldn't write, but he surrounded himself with the most important scholars of his time. In his Palatine Palace, where the town hall now stands, the medieval ruler celebrated and dined with his court according to strict rituals. Charlemagne ate first, then his guests. In 796 AD, he laid the foundation stone for the new cathedral where the German kings were later crowned. In 1978, Aachen Cathedral became the first German monument to be accepted as a UNESCO world heritage site.