wealth and influence, and Biržai was sold to the Tyszkiewicz family to cover debts in 1811. In 1849–1862, the Tyszkiewicz family built a neoclassic Astravas Manor palace across the lake from the site of the original castle. In 1869 the town had about 2,600 residents. Thirty years later the population had grown to 4,400. During World War II, the entire Jewish population of Biržai was annihilated. 15 Jews were shot to death by German soldiers at the Biržai Jewish cemetery in July 1941. On 8 August 1941, Gestapo and Lithuanian collaborators murdered the entire Jewish population of the town, some 2,400 people, by shooting them to death at a mass grave in a forest grove outside the town. The town was almost completely burned down during the war. Oldtown was destroyed. In 1968 the population reached 10,000. Currently there are 15,000 people living in Biržai. Architecture After the unrest and conflicts have settled down, from the 19th-century wooden residential houses prevailed and with an ongoing industrial revolution at the time, asbestos or metal-sheet roofing was common. With the majority of buildings being wooden, masonry buildings eventually emerged to battle cold winters and hot summers. In the early 20th century, central roads were cobblestone. During the World Wars, the old town was destroyed and the majority of wooden buildings in the main street burned down. During the Soviet rule, the town's population grew twice its previous size. To accommodate the growth, around 60 new apartment buildings were constructed and main streets asphalted. There was also an increase in new houses being built from bricks instead of wood, and the majority of them were left not plastered. With the help of European Union's Development Assistance grants, the town was able to regain a unique style - since 2014 numerous apartment building renovations were carried out with more planned, the road infrastructure is being improved and some new constructions built to attract visitors and to restore the historic appearance. Geography The northern part of the town, along with Lake Širvėna, lies within Biržai Regional Park. About 9,000 sinkholes have been identified in the park, formed abruptly after gypsum in the soil has been dissolved by underground water. Some of these holes are dry, while others have become small ponds or lakes filled with water from the many underground rivers and streams. New holes appear annually. According to local legend, the 20-meter-deep sinkhole known