Olbrück Castle is a hilltop fortress with a diamond-shaped floor plan. The central feature of the castle is the 34m high main tower, which dates back to the mid-14th century and is the oldest preserved part of the structure. Today, these rooms serve as museum spaces where visitors can learn about the construction history and function of castles. From the tower's roof, visitors have a panoramic view of the Rhine River to the east, the Ahr Mountains to the north, and the volcanic landscape to the south. On clear days, the Cologne Cathedral is even visible.
The castle was probably built originally in the 12th century. After several owners and reconstructions in the Late Middle Ages, During the Thirty Years' War, the castle was captured and devastated by Swedish troops in 1632. It was recaptured by Spanish and Electorate of Cologne troops under Graf Ernst von Isenburg-Grenzau in January 1633. Partially collapsed in 1660, the castle was subsequently restored under the supervision of Capuchin friar Bonitius from Linz.
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.