Nordhausen was first mentioned in records in the year 927 and became one of the most important cities in central Germany during the later Middle Ages. The city is situated on the Zorge river, a tributary of the Helme within the fertile region of Goldene Aue "(golden floodplain)" at the southern edge of the Harz mountains. In the early 13th century, it became a free imperial city, so that it was an independent and republican self-ruled member of the Holy Roman Empire. Due to its long-distance trade, Nordhausen was prosperous and influential, with a population of 8,000 around 1500. It was the third-largest city in Thuringia after Erfurt, today's capital, and Mühlhausen, the other free imperial city in the land.