Kraków contains also an outstanding collection of monuments of Jewish sacred architecture unmatched anywhere in Poland. Kraków was an influential centre of Jewish spiritual life before the outbreak of World War II, with all its manifestations of religious observance from Orthodox to Hasidic and Reform flourishing side by side. There were at least 90 synagogues in Kraków active before the Nazi German invasion of Poland, serving its burgeoning Jewish community of 60,000–80,000 (out of the city's total population of 237,000), established since the early 12th century.