This German city's location at the heart of the Sacred Roman Empire gave it a privileged economic position. It was the centre of all trading routes and therefore also a hub of artistic activity. The German Empire was a theoretical and constantly fluctuating body because of opposition to the Emperor from numerous Princes and Electors. Nuremberg's position as an Imperial city made it depend politically and economically on the Court. There were no craftsmen's guilds in the city which gave artists a certain degree of freedom in their dealings with potential clients. This made the creation of a patronage system similar to the Italian one possible. When the Reformation took place Nuremberg converted to Protestantism and the type of patronage changed, becoming more intellectualised and less ostentatious. It was also an important scientific centre, especially for astronomy and astrology, because the necessary instruments for both disciplines could be found in all the city's trading establishments. Another of the city's attractions was its dedication to printing and in 1496 it was the most important and most active centre in Europe. The professionals were divided between printers and image carvers, who specialised in preparing the blocks of wood for the presses. The introduction of engraving, printing using metal plates, was supported by the flourishing precious metal craftsmanship industry and the trade in these metals. There were precious metal mines near the city which were exploited and the products exported all over Europe. Nuremberg was governed by a Town Hall in which all the noble families were represented, of which there were forty-two in the 16th century. Under them were the honourable class and then the craftsmen, traders, manual workers and so on. The city had two parish churches, numerous chapels and secondary altars. The religious change gave rise to the restoration of altars and church ornamentation. The same happened in the Town Hall after Maximilian I's death on the occasion of Charles V's coronation, with the updating of the frescos in the meeting room, repainted with scenes alluding to the new Emperor.