a separate town), and Chwaliszewo (then a separate island) in 1444. The city also suffered from frequent epidemics of disease, which slowed the growth of the population. It also suffered a number of fires (particularly in 1386, 1447, 1459, 1464, 1536 and 1590), which increased the popularity of brick over wood as a building material. Floods were another frequent problem. The city's fortifications were strengthened from 1431 onwards, with the addition of wall towers, a tall observation tower and a second line of walls, a moat being created between the two lines. The city had a significant Jewish community, which had probably existed since the mid 13th century, although the first documentary record of them dates from 1367, by which time Poznań already had a synagogue. The Jewish quarter was in the north-east of the walled city, around the street called ulica Żydowska ("Jewish Street"), known as ul. Tkacka ("Weavers' Street") before the 15th century. The Lubrański Academy was founded in Poznań in 1519, Poland's second institution of higher education after the Jagiellonian University, although it did not have the right to award academic degrees. In 1536 the city suffered a major fire. The town hall was one of the buildings affected; the damage led to a major redesign and reconstruction of the building in 1550–1560, under the direction of Giovanni Battista di Quadro. In 1549 it is recorded that there were 550 houses belonging to the townspeople, 86 belonging to Jews, about 30 belonging to nobles and a similar number belonging to clergy. Many craftsmen by that time had moved to the settlements outside the city walls, leading to an increase in the number of residential buildings in the city. However many of the nobles' and clergy's possessions, both within and outside the walls, had the status of jurydyka, which placed them outside the control of the city and thus reduced the city's revenues and power. The Jewish quarter was also self-governing. It is estimated that the conurbation's population in this period was approximately 20,000, of which 8,000 lived within the city walls. However the population was subject to large fluctuations due to fires, floods and outbreaks of disease. At the end of the 16th century Poznań was a major centre for the fur and leather trade, particularly in skins coming from Lithuania and Russia. During the free election period in Poland, Poznań, as one of the most influential