Płock (pronounced ) is a city in central Poland, on the Vistula river, in the Masovian Voivodeship. According to the data provided by GUS on 31 December 2021, there were 116,962 inhabitants in the city. Its full ceremonial name, according to the preamble to the City Statute, is Stołeczne Książęce Miasto Płock (the Princely or Ducal Capital City of Płock). It is used in ceremonial documents as well as for preserving an old tradition. Płock is a capital of the powiat (county) in the west of the Masovian Voivodeship. From 1079 to 1138 it was the capital of Poland. The Wzgórze Tumskie ("Cathedral Hill") with the Płock Castle and the Catholic Cathedral, which contains the sarcophagi of a number of Polish monarchs, is listed as a Historic Monument of Poland. It was the main city and administrative center of Mazovia in the Middle Ages before the rise of Warsaw as a major city of Poland, and later it remained a royal city of Poland. It is the cultural, academic, scientific, administrative and transportation center of the west and north Masovian region. Płock is the seat of the Roman Catholic Diocese of Płock, one of the oldest dioceses in Poland, founded in the 11th century, and it is also the worldwide headquarters of the Mariavite Church. In Płock are located also the Marshal Stanisław Małachowski High School, the oldest school in Poland and one of the oldest in Central Europe, and the Płock refinery, the country's largest oil refinery. History Middle Ages The area was long inhabited by pagan peoples. In the 10th century, a fortified location was established high of the Vistula River's bank. This location was at a junction of shipping and routes and was strategic for centuries. Its location was a great asset. In 1009 a Benedictine monastery was established here. It became a center of science and art for the area. During the rule of the first monarchs of the Piast dynasty, even prior to the Baptism of Poland, Płock served as one of the monarchial seats, including that of Prince Mieszko I and King Bolesław I the Brave. The king built the original fortifications on Cathedral Hill (), overlooking the Vistula River. From 1037 to 1047, Płock was capital of the independent Mazovian state of Miecław. Płock has been the residence of many Mazovian princes. In 1075, a diocese seat was created here for the Roman