Frombork, the city where Mikolaj Kopernik (Nicolaus Copernicus) lived and worked, is located on the eastern bank of the Vistula Estuary. In 1329-1388 a cathedral of the Holy Virgin Mary and St. Andrew the Apostle was built on a hill towering over the town, and from the very onset became the prime church of the diocese of Warmia. In time, the cathedral was encircled with a system of walls, towers and defensive bastions. Mikolaj Kopernik was a canon of the Frombork chapter from 1507 until his death in 1543, and resided and worked on Cathedral Hill, where he conducted astronomical observations and wrote his momentous 'De revolutionibus...'. Although the memory of Kopernik continued to be cultivated uninterruptedly, not until 1916 was a small museum organised upon the initiative of Eugeniusz Brach Vogel, a canon of the Frombork chapter and an outstanding historian. The exposition was featured in a defensive tower, which belonged to the astronomer and burned down together with the majority of the historical buildings on the Hill in February 1945, after the arrival of the Red Army. Once this part of former Eastern Prussia was taken over by the Polish government administration and the diocese of Warmia - by the Apostolic Administration, work was inaugurated on putting Cathedral Hill into order. Immediately afterwards, upon the initiative of Stanislaw Lorentz, the then director of the National Museum in Warsaw, the least damaged buildings on the Hill were restored to be adapted for the Mikolaj Kopernik Museum. The Museum's seat was to be composed of the canonry of the Holy Virgin Mary (seventeenth-eighteenth century), the fifteenth-century House of the Custodian, and a fourteenth- century defensive tower, known since the seventeenth century as the Kopernik Tower. After the completion of indispensable repair-adaptation the post-war Mikolaj Kopernik Museum was opened to the public on 5 September 1948. The scarcity of original historical monuments associated with Kopernik and his activity inspired the restoration of the historical architectural complex on Cathedral Hill. The conservation commenced right after the war is continued up to this day. During the 1990s this historical complex was included onto the UNESCO World Heritage List. In time, the Mikolaj Kopernik Museum gained extremely valuable collections of old prints, including sixteenth-century works by Copernicus, astronomical instruments, and excellent works of art and the crafts. Once the Museum was transferred in 1970 to the rebuilt Old Bishop's Palace (fourteenth-eighteenth century) it was granted several new departments, i.a. astronomical, which conducts educational undertakings in a planetarium located in a fifteenth-century bastion. From 1981 the Museum also has its own astronomical observatory, situated near Cathedral Hill. Since 1989, following the incorporation of the historical Hospital of the Holy Ghost (fifteenth-eighteenth century) the Museum also contains a department on the history of medicine.