a Catholic church of the Holy Trinity, and from 1592 dedicated to Apostles Peter and Paul Roman Catholic Collegiate Church of the Holy Trinity (1635–1645) The Lutsk Gate of the city (1630s) Orthodox Christian Church of the Presentation in the Temple (1784) Orthodox Christian Church of the Holy Trinity (1886) Other Radziwill estates Dubingiai Kėdainiai Biržai Castle Mir Castle Niasvizh Castle Jewish presence Pre-World War II Jewish presence in Olyka dates back to the 16th century, and in the late 17th century the Jewish community became one of the largest in the Volhyn Region. After the Cossack Chmielnicki Uprising of 1648, 20 out of 30 Jewish households survived. It was believed that the prayer by Rabbi David HaLevi Segal miraculously saved the Jewish and non-Jewish citizens of Olyka from the Cossacks' assault of 1651. Olyka was the cradle of the Olyker Hasidic dynasty that was founded by the famous Rabbi Hersh Leib Landa the first Olyker rebbe. He was followed by his son Rabbi Yosef (Yoseph) Dovid, who was followed by his son Rabbi Mordechai (he authored a book called Gedulas Mordechai). He was followed by his son Rabbi Shimon Shloima (he authored a book called Shekel Hakodesh, and was father-in-law of Rabbi Yochanan Perlow of the Karliner Dynasty), who was followed by his son Rabbi Alter Yosef (Yoseph) Dovid. In 1897 a total of 2,606 people – 50 percent of the total Olyka population – were Jews, and that amount increased when many Jewish refugees from nearby towns fled to Olyka during World War I. According to the 1921 census, the number of Jews living in Olyka had decreased to 2,086 individuals. The Holocaust Olyka's large Jewish community was completely destroyed during the Holocaust, including Nazi persecutions at the site of the Radziwill Fortress/Olyka Castle. It is an important place of Jewish memory. Rabbi Alter Yosef Dovid Landa and his family perished. Following the September 1939 Ribbentrop-Molotov Pact and German-Soviet Occupation of Poland, many Jewish refugees from central and western Poland settled in Olyka in the fall of 1939, as did 60 Jewish refugees from Czechoslovakia. Jewish organizations and institutions were forced to disband. After the German invasion of Ukraine in June 1941, as part of Operation Barbarossa, the German 6th Army entered Olyka, destroyed houses, killed 100 Jews, and kept the remaining Jews in an open ghetto. Around 150 Jews evacuated eastward; most Jews stayed in the ghetto.