One 13th century resident of this city wrote a dialogue between herself and God where different phases of her life represented parts of the Trinity. In addition to that author of The Flowing Light of Divinity, Mechthild, this was the home city of Jacob Pretorius the Elder. Its eponymous Recht provided a widely adopted model for municipal administration, and its cathedral houses a baptismal font and ancient pillars made from porphyry in addition to the eponymousEhrenmalbuilt by Ernst Barlach. It was acquired by Brandenburg in the Peace of Westphalia and had earlier been a major player in the Hanseatic and the Schmalkaldic Leagues. One traumatic event for this city came at the instigation of Pappenheim and resulted in the city's name being a synonym for merciless pillage. For 10 points, name this German city on the Elbe, which was brutally sacked by forces under Tilly during the Thirty Years' War.