Hachen Castle, built around 1000, initially owned by Count Ezzo, later passed to Otto von Northeim in 1060. In 1080, Otto's son gifted it to the Archbishop of Cologne, who granted it as a fief to the Counts of Dassel. In 1232, the Counts of Dassel sold it to the Counts of Arnsberg. After changing hands multiple times, it became property of the municipality of Hachen in 1839. The castle's significance waned from the 15th century onwards. Limited research on its architectural history includes findings from 1923 and 1978–1980, revealing a main castle area, bailey, shield wall, and various structures.
The Jan Hus Memorial stands at one end of Old Town Square. The huge monument depicts victorious Hussite warriors and Protestants who were forced into exile 200 years after Hus, and a young mother who symbolises national rebirth. The monument was so large that the sculptor designed and built his own villa and studio where the work could be carried out. It was unveiled in 1915 to commemorate the 500th anniversary of Jan Hus' martyrdom. The memorial was designed by Ladislav Šaloun and paid for solely by public donations.
Born in 1369, Hus became an influential religious thinker, philosopher, and reformer in Prague. He was a key predecessor to the Protestant movement of the sixteenth century. In his works he criticized religious moral decay of the Catholic Church. Accordingly, the Czech patriot Hus believed that mass should be given in the vernacular, or local language, rather than in Latin. He was inspired by the teachings of John Wycliffe.