The first earth and timber fort was raised in Ostróda (Osterode) by the Teutonic knights in the mid-13th century. It stood in the fork between the Drwęca river branches, replacing an earlier Prussian stronghold. Construction of a brick castle built on a stone foundation was started by the Ostróda Commander (Hauskomtur) around 1349. The old earth and timber fortress together with the unfinished brick castle were hit by a fire during a Lithuanian raid commanded by duke Kiejstut in 1381. Soon afterwards a new brick castle was built.
The convent castle was constructed on a square plan, 44.7 x 45.2 m externally. Originally it had four wings with an archway in the west wing. Recently, the castle has been restored in the shape it had after the fire in 1788. Three wings (south, wet and north) have been preserved, although they lack the topmost storey, which was used for defense and storage. Some researchers claim that the castle had a tower in the south-east corner. To the north, there was a sanitary tower, most probably connected with the north wing of the castle by a wooden walk. During the archaeological excavations at the castle, the bases of pillars were unearthed, which may have supported the wooden gallery leading to the sanitary tower. The south wing contained a chapel, the commander's quarters and a refectory. The remaining wings most probably held the chapter room, infirmary and dormitories for brother knights and guests. The communication within the castle was through wooden walks parallel to the internal sides of the walls. Rooms on the ground floor in the north and south wings have preserved original cross and ribbed vaults on arches supported by granite pillars (partly reconstructed), while the cellars underneath are topped with cross vaults on diagonal arches. After the battle of Tannenberg, for two months Ostróda castle remained in the hands of Duke of Masovia, Janusz Mazowicki, who received the castle from the Polish King Władysław Jagiełło. In September 1410 the castle returned to the Teutonic Knights. In 1629 the Swedish King, Gustav Adolph resided at Ostróda castle. For six years, from 1633 to 1639, the castle was ruled by the Silesian Duke of Legnica and Brzeg, John Christian.
In the great fire of Ostróda in 1788, the flames reached the castle, where large quantities of gunpowder were stored in the east wing at that time. Soon a gigantic explosion damaged the east wing and the castle roofs. Although the castle was rebuilt, it did not regain its previous shape - the east wing was not reconstructed and the whole castle was one storey lower. In the 19th century the walls were plastered and many extensions were added to the castle building. From 21st February to 1st April 1807 the castle hosted the French emperor, Napoleon Bonaparte. He arrived here to rest after the exhausting battle at Prussian Eylau, which was victorious for the French party but caused much bloodshed. A rather unexpected outcome of that brief stay at Ostróda castle was a number of arts objects documenting the event. The Ostróda Museum exhibits a replica of the painting by the French artist Marie Nicolas Ponce-Camus 'Napoleon promises his grace to Ostróda burgers. March 1807'; the original canvas hangs in the historic gallery at Versailles. Another exhibit at Ostróda Castle which commemorates Napoleon I is a silver medal 'Napoleon a Osterode', made by the French graver Bertrand Andrieu. In the 19th century the castle was a seat for the local administration office and court of justice. There were also several apartments for officials. In 1945 the castle was burnt by the Soviet Army and remained in the state of preserved ruin for nearly thirty years. The reconstruction of the castle was commenced in 1974 and continued until the 1990s. At present, the castle houses the Museum of Ostróda, the Centre of Culture, a gallery and a library.References:
The Château de Chaumont was founded in the 10th century by Odo I, Count of Blois. The purpose was to protect his lands from attacks from his feudal rivals, Fulk Nerra, Count of Anjou. On his behalf the Norman Gelduin received it, improved it and held it as his own. His great-niece Denise de Fougère, having married Sulpice d'Amboise, passed the château into the Amboise family for five centuries.
Pierre d'Amboise unsuccessfully rebelled against King Louis XI and his property was confiscated, and the castle was dismantled on royal order in 1465. It was later rebuilt by Charles I d'Amboise from 1465–1475 and then finished by his son, Charles II d'Amboise de Chaumont from 1498–1510, with help from his uncle, Cardinal Georges d'Amboise; some Renaissance features were to be seen in buildings that retained their overall medieval appearance. The château was acquired by Catherine de Medici in 1550. There she entertained numerous astrologers, among them Nostradamus. When her husband, Henry II, died in 1559 she forced his mistress, Diane de Poitiers, to exchange Château de Chaumont for Château de Chenonceau which Henry had given to de Poitiers. Diane de Poitiers only lived at Chaumont for a short while.
Later Chaumont has changed hands several times. Paul de Beauvilliers bought the château in 1699, modernized some of its interiors and decorated it with sufficient grandeur to house the duc d'Anjou on his way to become king of Spain in 1700. Monsieur Bertin demolished the north wing to open the house towards the river view in the modern fashion.
In 1750, Jacques-Donatien Le Ray purchased the castle as a country home where he established a glassmaking and pottery factory. He was considered the French "Father of the American Revolution" because he loved America. However, in 1789, the new French Revolutionary Government seized Le Ray's assets, including his beloved Château de Chaumont.
The castle has been classified as a Monument historique since 1840 by the French Ministry of Culture. The Château de Chaumont is currently a museum and every year hosts a Garden Festival from April to October where contemporary garden designers display their work in an English-style garden.