Giecz was once one of the main centres of Polish statehood in the early Middle Ages, alongside Poznań and Gniezno.

In the early 9th century, a small keep was built on a mound on a peninsula on the Giecz lake; fortified with a stockade and earthworks.

The place quickly recovered and by the 13th century was a centre of administration, trade and commerce in the Greater Poland region.

After 1945, archaeologists discovered the remnants of a mediaeval pallatium, a pre-Romanesque rotunda, stone walls, a 13th-century palace and several sites of primitive iron-ore working.

Features of this settlement include open earthen structures, hearths, storage pits, and rich culture layers.