Duchy of Opole

State · 1177–1304 CE · at its largest around 1210 CE

Silesian duchy in Upper Silesia around Opole, ruled by a branch of the Silesian Piasts.

On its lands while it lasted

Opole (c. 1177 CE): Capital of Duchy of Opole (1177–1304).
Bytom (1200 CE): Capital of Duchy of Bytom (1285–1304).
Kalisz (c. 1210 CE): Capital of Duchy of Kalisz (1210–1219).
Kaliningrad (1255 CE): Capital of Duchy of Prussia (1526–1618).
Königsberg (1255–1945 CE): Capital of Duchy of Prussia (1526–1618), Brandenburg-Prussia (1619–1701).
Malbork Castle (1274 CE): Brick castle begun by the Teutonic Knights in 1274, later the order's headquarters; the largest castle in the world by land area.
Racibórz (c. 1285 CE): Capital of Duchy of Racibórz (1285–1304).