springs and also for strategic reasons as it is located between the Rhineland and northern France. Einhard mentions that in 765–766 Pepin spent both Christmas and Easter at Aquis villa (), ("and [he] celebrated Christmas in the town Aquis, and similarly Easter") which must have been sufficiently equipped to support the royal household for several months. In the year of his coronation as king of the Franks, 768, Charlemagne came to spend Christmas at Aachen for the first time. He remained there in a mansion which he may have extended, although there is no source attesting to any significant building activity at Aachen in his time, apart from the building of the Palatine Chapel (since 1930, cathedral) and the Palace. Charlemagne spent most winters in Aachen between 792 and his death in 814. Aachen became the focus of his court and the political centre of his empire. After his death, the king was buried in the church which he had built; his original tomb has been lost, while his alleged remains are preserved in the Karlsschrein, the shrine where he was reburied after being declared a saint; his saintliness, however, was never officially acknowledged by the Roman Curia as such. In 936, Otto I was crowned king of East Francia in the collegiate church built by Charlemagne. During the reign of Otto II, the nobles revolted and the West Franks under Lothair raided Aachen in 978. Aachen was attacked again by Odo of Champagne, who attacked the imperial palace while Conrad II was absent. Odo relinquished it quickly and was killed soon afterwards. The palace and town of Aachen had fortifying walls built by order of Emperor Frederick Barbarossa between 1172 and 1176. Over the next 500 years, most kings of Germany destined to reign over the Holy Roman Empire were crowned in Aachen. The original audience hall built by Charlemagne was torn down and replaced by the current city hall in 1330. The last king to be crowned here was Ferdinand I in 1531. During the Middle Ages, Aachen remained a city of regional importance, due to its proximity to Flanders; it achieved a modest position in the trade in woollen cloths, favoured by imperial privilege. The city remained a free imperial city, subject to the emperor only, but was politically far too weak to influence the policies of any of its neighbours. The only dominion it had was