The bishop castle of Haapsalu was built in the 13th century. It was the main residence of the Bishop of Läänemaa. The Läänemaa bishopric was created as a state of the Holy Roman Empire on 1 October 1228.
Construction, widening and reconstruction of the stronghold went on throughout several centuries, with the architecture changing according to the development of weapons. The stronghold achieved its final dimensions under the reign of Bishop Johannes IV Kievel (1515–1527). The western side of the castle houses a 29-metre watchtower dating from the 13th century, later used as a bell tower. The walls were later raised to 15 metres. The inner trenches and blindages, which were built for cannons and as a shelter from bombing, date back to the Livonian War (1558–1582), but it was during this war that the stronghold was severely damaged. The walls of the small castle and the outer fortification were left partly destroyed.
In the 17th century, the castle was no longer used as a defensive building by the Swedes who now ruled the Swedish Estonian Province. In the course of the Great Northern War in 1710, Estonia fell under Russian rule and the walls were partially demolished at the command of the Peter I of Russia, turning the castle in effect into ruins.
The Cathedral of Haapsalu is attached to the castle. It was the official chair of the Bishop, was situated and where the Chapter of the Bishopric worked. It is the biggest single-naved church in the Baltic countries, with its 15.5-metre-high domical vaults and an area of 425 m2. The Dome church was probably built in the 1260s, following the style of the Cistercian Order. The round baptism chapel on the eastern side of the church was built in the 14th or 15th century and is the site of a famous legend. On moonlight August nights the shape of a Lady in White appears on the inside wall of the chapel as the moon shines through the chapel window. This Lady is said to have been a woman who was in love with the abbot and entered the castle against his orders, therefore having been walled in there alive as a punishment. The church has been restored and it is again in active use by the local congregation of the Estonian Lutheran Church since 1990.
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.