of the largest and most significant Jewish communities in the world. Polish monarchs of the Piast dynasty invited the Jews to the country awarding them rights of status and total religious tolerance. By the mid-16th century, 80% of the world's Jews lived in Poland. Thanks to a long period of Polish statutory religious tolerance and social autonomy, the immigration of Jews to Poland began to increase already during the Crusades because of systemic persecution of Jews in Western Europe. Jewish settlers built their own settlements in Poland. By the mid-14th century they had occupied thirty-five towns in Silesia alone. The Catholic Church, however, was opposed to the tolerant attitude of the Polish royalty. The 1266 council of Breslau applied the Fourth Council of the Lateran limitations on the Jews to the Roman Catholic Archdiocese of Gniezno, forbidding side-by-side life of Jews and Christians and setting up Jewish ghettos. In large cities, residential quarters were assigned to them, as found, for example, in Kazimierz, later a prominent district of Kraków. In the Kazimierz city, a 34-acre "Jewish Town" was set up by king Jan I Olbracht in 1495 for the relocation of Jews from Kraków Old Town after a citywide fire. Kraków's Kazimierz is one of the finest examples of an old Jewish quarter to be found anywhere in the world. The Jewish quarter was governed by its own municipal form of Jewish self-government called kehilla, a foundation of the local qahal. In smaller Polish towns, ethnic communities were mostly integrated. The Holocaust Nearly complete genocidal destruction of the Polish Jewish community took place during the German occupation of Poland and the ensuing Holocaust. The World War II ghetto-system had been imposed by Nazi Germany roughly between October 1939 and July 1942 in order to confine Poland's Jewish population of 3.5 million for the purpose of persecution, terror, and exploitation. The Warsaw Ghetto was the largest ghetto in all of Nazi occupied Europe, with over 400,000 Jews crammed into an area of , or 7.2 persons per room. The Łódź Ghetto (set up in the city of Łódź, renamed Litzmannstadt, in the territories of Poland annexed by Nazi Germany) was the second largest, holding about 160,000 inmates. Over three million Polish Jews perished in World War II, resulting in the destruction of an entire civilization. A more complete list of over 260 ghettos with approximate number of prisoners, date of creation