throughout the empire experienced infrastructure improvements: improved roads and exchange regulations encouraged trade, particularly in the all important centrally located Swabia. The exact date in which the city received its market rights is ambiguous, but it was probably between 1180 and 1191; maps showing the trading road from Stockach to Buchhorn show the city of Überlingen in comparable size and type; by 1226 Überlingen had a Jewish cemetery, and these clues lead to the conclusion that the city had a market for a much longer period than this, thus the supposition that the Emperor Barbarossa had established the market at the end of his own regime. He had been in the region several times: 1153, 1155, 1162, 1181, 1183, to hold court sessions, and in 1187 he stayed in Wallhausen, across the lake, to sign the documents establishing the Cloister of Salem. At the end of the 14th century the city was granted status as a free imperial city. In 1547, the Holy Roman Emperor, Charles V, broadened the city's market rights to prohibit any trade in grain or salt within two German miles (about 15 km or 10 English miles) of the city. Early modern period The city flourished in the 13th to 16th centuries mainly due to widespread grapevine cultivation on the south-facing slopes of the Lake Constance and its salubrious climate, which gave rise to a profitable spital (hospital) industry. The Holy Ghost Spital in Überlingen held large landholdings in Upper and Lower Linzgau, and in the Hegau. The city's affluence encouraged the construction of an impressive religious building: the St Nikolaus Munster in the late 15th century; a City Hall in the late 15th century; and impressive residences for the family of the spital doctors. The relative affluence of the city has been documented in its art and architecture, and the size and solidity of its physical plant, especially its fortifications. As a fortified bridgehead, the city proved vital to the reduction of the German Peasants' War in 1525. When Georg Truchsess von Waldburg's soldiers rose against him during the war, and besieged Radolfzell, the Burgermeister of Überlingen led a small force to free the nearby town; they returned with 150 prisoners, all of whom were executed in a single day by the city's executioner. As a result of this assistance, Überlingen was granted the right to quarter a shield with a drawn sword, the Habsburg