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.
House of the Blackheads (Melngalvju nams) is a building situated in the old town of Riga. The original building was erected during the first third of the 14th century for the Brotherhood of Blackheads, a guild for unmarried German merchants in Riga. Major works were done in the years 1580 and 1886, adding most of the ornaments.
The structure was bombed to a ruin by the Germans June 28, 1941 and the remains demolished by the Soviets in 1948. The current reconstruction was erected from 1995 to 1999. Today the House of Blackheads serves as a museum and sometimes concert hall.