The historical Old City of Siegen, the former butcher and tanner neighborhood, distinguishes itself through buildings constructed in the timber-frame style typical for the region and period. The slate-covered timber-frame houses as an unusual black-and-white painting let the medieval times come alive once again in the narrow streets. Integral parts of the Old City are the largely perserved city wall; the churches, such as the protestant Martini Church, which dates back to the 10th Century and used to constitute the center of the Old City; and the museums. The lower castle (Untere Schloss), which contains a prince's crypt and the upper castle (Obere Schloss) including the castle park and Siegerlandmuseum rank as Siegen's key architectural monuments. The upper castle contains original paintings by Peter Paul Rubens, who was born in Siegen.