Amber, the fossilised resin of coniferous trees, has been used to produce jewellery and taken as a medicinal compound for many centuries. This mineral is found all over the world but the southern and eastern shores of the Baltic Sea are blessed with especially large deposits of top quality amber. Roman merchants also made their way here in ancient times. There were two amber roads in the early middle ages - a western (Jutland) road and an eastern (Sambia) road. These were marked out in the 1^st century A.D. and carried their greatest traffic between the 1^st and 3^rd centuries A.D. The Amber Road is now generally believed to have been one of the most important trade routes in Europe at the time, comparable to the famous Silk Road which led into the heart of Asia.

The modern city of Kalisz, whose existence is attested by written sources dating back 1,800 years, lay on the amber road. Between 142 A.D. and 147 A.D., the scholar Ptolemy (c. 90 A.D. - c. 168 A.D) registered a settlement named "Kalisia" on a map in his work Geographia and determined its coordinates. The researcher presumably drew on the reports of Roman merchants and the records of Marinus of Tyre. The tradition of calling Kalisz the oldest city in Poland came into being based on this evidence, supported by the suppositions of the 15^th century chronicler Jan Długosz. Later researchers noticed a similarity with the name "Halisia", which the Roman historian Tacitus mentions in his Germania.