The first wooden mansion in Oporów was probably built in the middle of the 14th century. The brick castle was erected in the years 1434-1449 by the bishop of Kujawy, Władysław Oporowski, although it is possible that the first works were taken during the life of the voivode Mikołaj Oporowski in the beginning of the 15th century. The castle was the center of the vast estates of the Oporowski family of the Sulima coat of arms.
At the beginning of the 17th century, the castle was taken over by the Tarnów family, coat of arms of Rola, then Sołłohub, Korzeniowscy, Pociejów, the Orsettis family and the Karscy family. Renovations made in the seventeenth, eighteenth and nineteenth centuries caused only minor alterations. From around 1840, there is an annex in the courtyard, so-called “Kredens” and the neo-gothic portal of the entrance gate and terrace in front of the bridge. Thorough conservation works made in the years 1962-1965 removed some of the reconstruction from the 19th century, restoring the original silhouette of the roofs and the porch of the residential house. Portals, gothic windows and wooden, polychrome ceilings were unveiled from the plaster.
The castle occupies the center of a small mound surrounded by a watery moat. It is a brick stronghold on the foundations of glacial erratic stones. In the first phase a four-sided, four-storey tower was built with two buttresses. In the second phase from the beginning of the 15th century it was included in the quadrilateral of the perimeter walls, and to the south there was a gateway. At the same time, it was planned to build a residential house at the eastern wall, but this intention was never implemented. In the third phase, a southern house was erected, and a wooden house was erected next to it. At that time, a second tower was built on the eastern wall, housing the chapel.
Thus, the castle was finally built on an irregular quadrilateral plan measuring 25×30 meters, consisting of buildings grouped around a small courtyard: a one-story southern home with dimensions of 8,5×23,5 meters, a four-sided western tower measuring 8,3×9,6 meters and a tower with a chapel located on the axis of the eastern curtain.
The castle now houses a museum with an exhibition of court interiors. It is made up of works of art and handicraft products that present nobility culture. The collections contain works of art from various periods, from the 16th to the beginning of the 20th century. It is open every day from 10:00 to 16:00 and in spring and summer from 10:00 to 17:00.
Leksykon zamków w Polsce, L.Kajzer, S.Kołodziejski, J.Salm, Warszawa 2003.