Town fortifications were demolished. The moat encircling the walls was filled in and turned into a green belt known as Planty Park. History The first mention of Kraków dates back to the second half of the ninth century. By the end of tenth century the city was incorporated into the Polish state under the rule of Piast dynasty. The episcopal bishopric was awarded to Kraków in 1000 and around that time, it became the residence of Polish kings for centuries to come. The history of the old city of Kraków revolves mainly around its Old Town District of today. Here, the regalia were stored and, back in early Middle Ages, a cathedral school was erected. Around 700 A.D., local tribes initiated the process of forming the Vistulan State by uniting with each other. Numerous remains of a once massive earth embankment encircling Wawel Hill survived till this day. A chest with 4,200 iron axes weighing about 4 tons was found in a basement of a house at Kanoniczna 19 street. These axes were commonly known under the name of "płacidłos" which is a word derived from the Polish verb "płacić" – to pay. As it happens the axes were a main legal tender in the neighboring Great Moravian State. The value of the treasure chest is the greatest to be discovered thus far and testifies to Kraków's significant wealth and power in the region. At Wawel's foot, in the place where now Kanoniczna, Grodzka and other neighboring streets are located, remains of a Vistulan settlement called Okół were found. This settlement, the beginnings of which can be dated at least back to the early ninth century, was surrounded by an enormous oak palisade and, in the place where now the Straszewska and St. Gertrude's streets run, by one of Vistula's arms. Near Main Market Square – specifically near Church of St. Wojciech and Church of St. Mary and Bracka street - another discovery was made. Found here were the relics of craft workshops and of dwelling houses which were originally raised near Vistula. What is more, under St. Wojciech's Church parts of a wooden temple were discovered. In those days Vistula had many arms which in turn formed several little islands in Kraków's centre. Kazimierz was one of such islands. It is also possible that Okół, Wawel and the Main Market Square were islands separated from the mainland by moats