Complex sentence: Of the more than 110 synagogues in Iași before World War II, the Great Synagogue remains a witness of the Holocaust, and it is one of only two which continues to serve the dwindling Jewish community of Iași.
Split into simpler sentences: Of the more than 110 synagogues in Iași before World War II, only the Great Synagogue remains as a result of the Holocaust. The synagogue is one of only two which continues to serve the dwindling Jewish community of Iași.