While it may look rather unassuming in the 21st century, Giecz was once one of the main centres of the early Piast state 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. Since 940 it was one of the key strongholds of the early Piast dynasty. In 1038 during a war with Bohemia, the place was seized by Bretislaus I, who sacked the nearby settlement and sold its inhabitants into slavery. The place quickly recovered and by the 13th century was a centre of administration, trade and commerce in the Greater Poland region. At about that time, the settlement received a town charter and became the seat of a castellany. However, in 1331, it was burnt to the ground, never to recover. The museum in Giecz is part of the Museum of the First Piasts, based near Ostrów Lednicki in Dziekanowice.