1155 – The first written mention of Cieszyn -
Cieszyn as Tescin was mentioned in the manuscript sources for the first time in Pope Hadrian IV’s bulla issued in Rome in 1155 for Walter, bishop of Wrocław. This document confirms the important function of the town on the Olza River, which was the capital of a castellany, that is, the then administrative unit of middle rank in Silesia. The next mention of the town, at that time called Tessin, comes from 1223. At the end of the 13th century, the town was called Teschin.