Giecz, one of the main strongholds of the Piast monarchy, alongside Poznań, Gniezno, Ostrów Lednicki and Łekno, was constructed in the second half of the 9th c. to the south of the mentioned fortresses. The enlargement of the centre took place in the second half of the 10th c. The invasion of the Czech Duke Břetislav and resettling of inhabitants of the stronghold to Bohemia in 1039 impeded the development of Giecz. However, the destroyed stronghold was rebuilt and restored to its previous splendour. Until the turn of the 13th and 14th c. Giecz was a seat of the castellany. Then, it lost its importance in favour of towns which were coming into existence in the neighbourhood and it fell into oblivion. On the basis of examinations held after World War II it is known that the stronghold in Giecz had a great strategic significance and played an important role in trade exchange. Medieval ramparts of the stronghold, which are up to 7 metres high, survived in a very good shape. Inside the stronghold, near the main entrance, it is possible to see the stone foundations of a palatium with an attached rotunda-shaped chapel. The remains of one of the earliest churches in Poland have been recently discovered in the northern part of the stronghold. The church had a double-tower westwork, which is typical for the form of German churches originating in the sphere of the Carolingian architecture.

In a museum exhibition building inside the stronghold it is possible to visit a permanent exhibition “Terra sancta – Giecz in the Piast Monarchy.” It displays finds from archaeological excavations in the area of the stronghold and its vicinity. Some of these, e.g., a sword or a conical helmet, are unique in their nature. Other ones, such as ornaments from bone, antler, silver, gold or semi-precious stones, confirm the rank and exceptional nature of the stronghold centre in Giecz.

In front of the stronghold there is a reconstruction of a Medieval settlement, surrounded with a palisade. It comprises a farmer’s homestead, a herbalist’s hut or a fisherman’s stilt house. Educational activities for children and school youth, as well as open air events related to the Slavic ceremonial year, are held in the area of the settlement. Another exhibition building for temporary exhibitions was also built here.

In the museum there is a sales point with souvenirs and museum publications.