There has been a fortified hill in Lieto (“Liedon Vanhalinna”) from the prehistoric age. According to excavations, the castle has been in use in the Late Bronze Age (1500-500 BC), in Middle Iron Age (500-700 AD, contested) and in the Middle Ages up to the end of the 14th century, when it was replaced by the "new castle" in Turku harbour.
During the first crusade (ca. 1155) to Finland Swedish army fought heavy battles against pagan Finnish people to conquer Lieto castle hill. After the victory Swedish fortified hill with stone and brick walls to defence the new city of Turku and christianity against Finnish and Novgorodians. There were several buildings, outer walls and a watch tower in the hill. When the Turku castle was completed Lieto castle lost the military value and was left to decay. The latest record of the existing castle date from the year 1438.
In the 1956 private landowners donated Lieto hill to the University of Turku, which has used hill for the archeological training. Nowadays there are some few ruins left of castle walls and buildings.
German crusaders known as the Livonian Brothers of the Sword began construction of the Cēsis castle (Wenden) near the hill fort in 1209. When the castle was enlarged and fortified, it served as the residence for the Order's Master from 1237 till 1561, with periodic interruptions. Its ruins are some of the most majestic castle ruins in the Baltic states. Once the most important castle of the Livonian Order, it was the official residence for the masters of the order.
In 1577, during the Livonian War, the garrison destroyed the castle to prevent it from falling into the control of Ivan the Terrible, who was decisively defeated in the Battle of Wenden (1578).
In 1598 it was incorporated into the Polish-Lithuanian Commonwealth and Wenden Voivodship was created here. In 1620 Wenden was conquered by Sweden. It was rebuilt afterwards, but was destroyed again in 1703 during the Great Northern War by the Russian army and left in a ruined state. Already from the end of the 16th century, the premises of the Order's castle were adjusted to the requirements of the Cēsis Castle estate. When in 1777 the Cēsis Castle estate was obtained by Count Carl Sievers, he had his new residence house built on the site of the eastern block of the castle, joining its end wall with the fortification tower.
Since 1949, the Cēsis History Museum has been located in this New Castle of the Cēsis Castle estate. The front yard of the New Castle is enclosed by a granary and a stable-coach house, which now houses the Exhibition Hall of the Museum. Beside the granary there is the oldest brewery in Latvia, Cēsu alus darītava, which was built in 1878 during the later Count Sievers' time, but its origins date back to the period of the Livonian Order. Further on, the Cēsis Castle park is situated, which was laid out in 1812. The park has the romantic characteristic of that time, with its winding footpaths, exotic plants, and the waters of the pond reflecting the castle's ruins. Nowadays also one of the towers is open for tourists.