(Virchow 1877) or a pile dwelling on the island (Bielenstein 1970). Lowering the level of the lake in 1965 helped researchers to discover the structure of the fortress. The surface of the island was covered by a horizontally laid thick lattice of logs that covered an area about twenty-eight by thirty-five meters. Remains of 145 wooden constructions—dwellings and fortification systems of five phases of habitation—were discovered lying directly one over the other without any archaeological break. The dwellings of the first stage were built in a.d. 830 and the dwellings of the third stage in a.d. 890. These were timber log dwellings, of yoke-angle construction. The buildings of the first three stages were built in the center of the fortress, but during the fourth and fifth stages buildings were also located along the perimeter of the settlement. The unique reconstruction of the fortress Āraiši was elaborated on by Jānis Apals and architect Dzintars Driba (1987–1992). Reconstruction was finished in the 1980s. The Open Air Museum on island Āraiši was organized by the Inspection of Monument Protection at the Ministry of Culture of Latvia and the Foundation of the Āraiši Lake Fortress.

Daugmale, at 3,800 square meters, is one of the largest hillforts in Latvia. The town covered two hectares and included a port (ninth through twelfth centuries a.d.) in the lower flow of the Daugava River. Daugmale was inhabited by Semigallians in the ninth century and by Livs in the tenth through the twelfth centuries. It was an economic, political, cultural, and transit trading center, as well one of the largest craft centers (iron, bronze, bone, antler, amber, and pottery processing) of the Livs before the adoption of Christianity in the thirteenth century.

Dreng‘eri-čunkāni, the largest investigated cemetery of the Semigallians of the seventh through the tenth centuries a.d., lies in the southeastern part of Semigallia. Excavations in 1982 through 1991 by Māris Atgāzis and Viktorija Bebre discovered 697 graves in lines without the secondary filling of the territory of cemetery with new deceased individuals. It is evidence of the peaceful development of Semigallian society in the period before the first Catholic bishops came from Germany and fought for the adoption of Christianity among the pagan natives.

Jersika (Gersike) was the Lettgallian (letti, letthigali) economic, political, and cultural center in the tenth through the twelfth centuries a.d. It sits on the sixteen-meter-high bank of the middle flow of the Daugava River between two valleys. Jersika is one of the best-fortified hillforts, with a defensive system built up by an oak log rampart. Inside are camera-shaped buildings full of earth and stones. The area of the flattened plateau was 100 meters by 75 meters. Jersika was the residence of Wissewalduc, Rex de Gerceke (Heinrici Chronicon, XXIX.4), who displayed great resistance to the Catholic bishops, including Albert, during the adoption of Christianity. Jersika was burned twice between a.d. 1209 and 1215 by Crusaders. The Lettgallians lost their independence gradually. In a.d. 1239 Jersika was only a locum castri (local camp). Archaeological excavations carried out by Francis Balodis (1939) and Antonija Vilcāne (1995–1999) revealed that the hillfort had been burned down.

Lubāna Lake Wetland lies in the middle part of the East Latvian lowland. It is a region of concentration of Stone Age settlements (30 units), which were discovered in the 1960 and 1970s. The wetland was the main region of postwar excavations of Stone Age settlements, and boasts well-preserved organic materials. It is the best region for elaborating Stone Age chronology (70 radiocarbon data) and for reconstructing subsistence strategy and cultural development in Latvia during the period from 7110 to 3640 b.p. It was the main center for amber processing in the inland territories of the eastern Baltic during the Neolithic period.

The Lubāna Lake Collection contains more than 3,000 stray finds of late Paleolithic, Mesolithic, and Neolithic bone and antler artifacts. The collection was gathered from the bottom of Lake Lubāna by local people between 1937 and 1939 after the water level was lowered and includes harpoons, slotted points, spearheads, daggers, knives, arrowheads, fishhooks, and cult objects. The collection was subsequently passed into the hands of the Board of Antiquity in Rīga.