By the 13th century, Brno began to grow more quickly. The trading settlements near the castle grew, into what is now the city's Old Town and Upper Market districts. In addition to the Slavic farming villages and manorial houses, the town also attracted a growing population of foreign merchants of German, Flemish and Walloon origin to form the Lower Market, as well as a Jewish community. The growth was aided further by the granting of City Charter in 1243. Soon after, the manorial seat of the margraves moved from the castle on Petrov hill to to one on Spilberk hill, a castle that became infamous as a prison for dissident nationals of the Hapsburg Empire after the 17th century. The site of the first castle became the location of the Cathedral of St. Peter and Paul, which joined the older church of St. James, supposedly first built in 1220, as the dominant churches of the city. Brno, along with the rest of the Czech lands, prospered as a crossroads for trade at the center of Europe and continued to grow into the 14th century, alternating with the city of Olomouc as the seat of the Moravian Congress, an assembly of regional government with political, legal and economic desicion-making powers. One of the privileges granted to the city through its charter was the hosting of an annual trade fair, which contributed to the growth of international trade. This tradition continues to the present day, with the Brno Trade Fair grounds hosting a large number of international trade fairs every year, including well-known automobile and computer exhibitions. The following centuries of military conflict brought invaders to the walls of Brno repeatedly, from the Hussite Wars of the Protestant Reformation and the civil wars of royal accession in the 15th century, to the threat of Turkish invasion in the 16th century and the blight the Thirty Years brought to the land in the 17th. The castle ceased to function as fortress during the Napoleanic Wars, and this brought about the transformation of the walls around Brno into a system of parks surrounding the historical center. Brno began to feel the effects of the Industrial Revolution early in the 19th century, primarily in the textile industry, and later in the manufacture of machinery. The technical development of its factories was equal with that of anywhere in the world, and its products were exported all throughout Europe. Iron foundries came into being, the foremost being the First Brno Machine Works, and later the Kralovopolska Machine Works. This development spurred the growth of Brno still further. In 1850, by government decree, the city expanded to incorporate 29 surrounding communities, producing a city of 50,000 overnight, a number that doubled by the turn of the century.