The city of Erfurt was, by the middle of the seventeenth century, the most important city in the central German heartland of Thuringia (Figure 1). With nearly 18,000 residents, Erfurt was the largest city in Thuringia and was the commercial and cultural capital of the region.1 Following the Thirty Years War and under the electoral archbishopric of Mainz, Erfurt became a uniquely ecumenical (i.e., bi-confessional) city, with nearly twenty percent of its residents worshipping as Roman Catholics.