Castle of Warmian Bishops in Olsztyn

In 1334 the Warmian land vogt Henryk von Luter raised a timber-and-earth watchtower in the land of Bertingen to shield settlers from Lithuanian raids. Around 1345 or shortly after, another Warmian vogt, Bruno von Luter, began a masonry castle nine kilometres north, in a defensible bend of the Łyna, and from 1346 or 1347 the Warmian Cathedral Chapter carried it on. At a council in the old watchtower in May 1348 the chapter resolved to found a town beside the new castle, and on 31 October 1353 granted Olsztyn its town charter, by which date the castle was most probably substantially finished; the chamber district moved its seat there.

The castle then had one main wing on the north-east side of a quadrangular courtyard, ringed by walls and a ditch and reached from the Łyna over a drawbridge. A second wing followed in the 15th century. The mid-14th-century tower was rebuilt in the early 16th, round on a square base and forty metres tall; the walls were raised to twelve metres, doubled with a lower outer ring of turrets and joined in part to the town walls, so that the castle stood in effect as a bastion thrust out beyond the town, guarding the way in.

The castle belonged to the Warmian chapter at Frombork; it was the seat of the Olsztyn chamberlain and lodged the administrator of the chapter's estates, one of the Frombork canons, during his visitations. It saw action early: on 21 January 1356 it held out against a large Lithuanian incursion under Kęstutis and Algirdas, who laid waste the chamber district around it. Lithuanian raids recurred until the end of the 14th century, so the town was fortified further and food stores kept in the castle.

Until 1454 all Warmia lay under the military protection of the Teutonic Order, which placed the castle in the path of the Polish-Teutonic wars. In 1410, after the battle of Grunwald, it surrendered to the Polish-Lithuanian army without a fight; Władysław Jagiełło installed a Polish garrison and made it over to Duke Janusz I of Masovia. In the Hunger War of 1414 it fell after a siege of several days, given up by Filip of Narzym, a knight of the anti-Teutonic opposition. Through the Thirteen Years' War of 1454-66 it passed from hand to hand, and after the Second Peace of Thorn in 1466 castle and Warmia lay within Poland for more than three hundred years.

From 1516 to 1521, with a short break, the administrator of the Olsztyn chamber district was Nicolaus Copernicus, a canon of the Warmian chapter at Frombork. He lived in the north-eastern wing, wrote his treatise on money there, observed the motion of the planets, and set on the cloister wall a table for following the spring and autumn equinoxes; that table of 1517 survives, probably his own work, and is reckoned the only preserved astronomical instrument he made and used. When the Teutonic Order threatened castle and town for the last time, in the Prussian war of 1521, Copernicus prepared the defence; it was effective enough that the Order broke off after a single failed assault.

The refectory and the administrator's chamber were given crystal vaults in the early 16th century. Two Warmian bishops who were also writers stayed there that century: Johannes Dantiscus, called the father of Polish diplomacy and crowned with the imperial laurel for his Latin songs, and Marcin Kromer, who wrote scientific and literary work in Latin and Polish with equal ease. In 1580 Kromer consecrated the chapel of St Anne, newly built in the south-western wing.

The wings lost their military value in time and made poor lodgings, so in 1758 a drive was brought up from the town and a palace wing built, clearing away the outer bailey and part of the walls. Ignacy Krasicki, bishop of Warmia and a leading Polish poet, stayed in 1779. After the First Partition and the secularisation of Warmia in 1772 the castle passed to the Prussian state.

In 1807 it held the Napoleonic headquarters; on 3 February Napoleon Bonaparte ate at the castle before the battle of Olsztyn, questioning the priest and historian Gerard Gley about traces of Copernicus. In 1845 the ditch was drained and the bridge replaced by a causeway.

A regional museum was installed in the castle rooms in 1921. In 1945 Warmia returned to Poland, the castle passed to the Polish state with most of its pre-war collection, and became the seat of the Museum of Masuria, today the Museum of Warmia and Masuria. It was entered in the register of monuments in 1953 and declared a Historic Monument on 8 September 2023.