Blackhammer Chambered Cairn is a Neolithic cairn on Rousay. It is thought to date from around 3000 BC. The structure is a typical stalled cairn, with an interior divided into seven compartments by pairs of upright stone slabs. The cairn has a modern roof, as the cairn originally was only a few feet high. Access is by a hatchway and ladder in the roof, as the original entrance was sealed. There have been finds of bones and pottery in the cairn.
References: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.