Loučeň Castle was built on the site of a former medieval fortress. The first mention of this fortress dates back to 1223 and was discovered in the testimonial of the Prague bishop Peregrinus. This year is also considered the first official mention of the village of Loučeň. From that time until 1618, several lords and peasants alternated as owners of the fortress.
In 1612, the castle of Loučeň and other adjacent villages were owned by Václav Berka of Dubá the Elder, a very wealthy nobleman who did not sympathize with Emperor Ferdinand II. Therefore, in 1620, after the Battle of White Mountain, Václav Berka left the country and the castle was confiscated in 1622 due to his participation in the anti-Habsburg uprising. A year later, all of Berka's property was purchased by Adam of Valdštejn.
During the Thirty Years' War, all the surrounding villages in the Nymburk region were heavily affected by the invasion of armies. The dilapidated fortress in Loučeň was not renovated until 1704-1713, when Karel Arnošt of Valdštejn began to transform it into a Baroque castle. A chapel was also added to the castle, which was later converted into the Church of the Assumption of the Virgin Mary. After Karel Arnošt's death, his daughter Eleanora took over the estate, and she passed it on to her daughter Maria Anna. She was very determined, persecuted evangelicals, and tightened the requirements of serfdom. Maria Anna married Josef Fürstenberg, and thus the ownership of Loučeň Castle passed from the Valdštejn family to the Fürstenbergs.
The first written record of church in Danmark locality date back to the year 1291. Close to the church are several stones with a Christian text and cross inscribed. The oldest parts of the present red-brick church are from the 1300s. In the late 1400s the church was enlarged to the appearance it has today. The church has been modified both internally and externally several times, among other things after the fires in 1699 and 1889. There are lot of well-preserved mural paintings in the walls.