A Slavic settlement on the great trade route between Scandinavia and Constantinople, Kyiv was a tributary of the Khazars,[12] until its capture by the Varangians (Vikings) in the mid-9th century.Coming under Lithuania, then Poland and then Russia, the city would grow from a frontier market into an important centre of Orthodox learning in the sixteenth century, and later of industry, commerce, and administration by the nineteenth.Its armament-dependent industrial output fell after the Soviet collapse, adversely affecting science and technology, but new sectors of the economy such as services and finance facilitated Kyiv's growth in salaries and investment, as well as providing continuous funding for the development of housing and urban infrastructure.[28] During the early Iron Age certain tribes settled around Kyiv that practiced land cultivation, husbandry and trading with the Scythians and ancient states of the northern Black Sea coast.The Primary Chronicle states that at some point during the late 9th or early 10th century Askold and Dir, who may have been of Viking or Varangian descent, ruled in Kyiv.[35] According to the aforementioned scholars the building of the fortress of Kyiv was finished in 840 under the leadership of Keő (Keve), Csák, and Geréb, three brothers, possibly members of the Tarján tribe.[50] Occupied by Russian troops since the 1654 Treaty of Pereyaslav, Kyiv became a part of the Tsardom of Russia from 1667 on the Truce of Andrusovo and enjoyed a degree of autonomy.Following the gradual loss of Ukraine's autonomy, Kyiv experienced growing Russification in the 19th century, by means of Russian migration, administrative actions, and social modernization.At the beginning of the 20th century the Russian-speaking part of the population dominated the city centre, while the lower classes living on the outskirts retained Ukrainian folk culture to a significant extent.[citation needed] However, enthusiasts among ethnic Ukrainian aristocrats, soldiers, and merchants made attempts to preserve the native culture in Kyiv, by clandestine book-printing, amateur theatre, folk studies, etc.Landmarks of that period include the railway infrastructure, the foundation of numerous educational and cultural facilities, and notable architectural monuments (mostly merchant-oriented).Allegedly in response to the actions of the NKVD, the Germans rounded up all the local Jews they could find, nearly 34,000,[57] and massacred them at Babi Yar in Kyiv on 29 and 30 September 1941.In total, there are 448 bodies of open water within the boundaries of Kyiv, which include the Dnieper itself, its reservoirs, and several small rivers, dozens of lakes and artificially created ponds.The June 2007 unofficial population estimate based on amount of bakery products sold in the city (thus including temporary visitors and commuters) gave a number of at least 3.5 million people.The March 1919 Kyiv city census, conducted by the Bolshevik authorities, showed an increase in the percentage of the population identifying as Ukrainian to 25%.[102] The plans of building massive monuments (of Vladimir Lenin and Stalin) were also abandoned, due to lack of money (in the 1930s–1950s) and because of Kyiv's hilly landscape.As a result, Kyiv's central districts provide a dotted contrast of new, modern buildings among the pale yellows, blues, and greys of older apartments.And most importantly, with the easing of the visa rules in 2005,[103] Ukraine is positioning itself as a prime tourist attraction, with Kyiv, among the other large cities, looking to profit from new opportunities.Many historic areas of Kyiv, such as Andriivskyi Descent, have become popular street vendor locations, where one can find traditional Ukrainian art, religious items, books, game sets (most commonly chess) as well as jewellery for sale.Other notable sites is the cylindrical Salut hotel, across from Glory Square and the eternal flame at the World War Two memorial Tomb of the Unknown Soldier, and the House with Chimaeras.Among Kyiv's best-known monuments are Mikhail Mikeshin's statue of Bohdan Khmelnytsky astride his horse near St. Sophia Cathedral, the venerated Vladimir the Great (St. Vladimir), the baptizer of Rus', overlooking the river above Podil from Saint Volodymyr Hill, the monument to Kyi, Shchek and Khoryv and Lybid, the legendary founders of the city at the Dnieper embankment.Kyiv also has numerous recreational attractions like bowling alleys, go-cart tracks, paintball venues, billiard halls and even shooting ranges.From 1 December 2008, the stadium underwent a full-scale reconstruction in order to satisfy standards put in place by UEFA for hosting the Euro 2012 football tournament; the opening ceremony took place in the presence of president Viktor Yanukovych on 8 October 2011,[115] with the first major event being a Shakira concert which was specially planned to coincide with the stadium's re-opening during Euro 2012.Since introducing a visa-free regime for EU-member states and Switzerland in 2005, Ukraine has seen a steady increase in the number of foreign tourists visiting the country.Because the city has a large and diverse economic base and is not dependent on any single industry or company, its unemployment rate has historically been relatively low – only 3.75% over 2005–2008.[126][127][128] Kyiv is the undisputed center of business and commerce of Ukraine and home to the country's largest companies, such as Naftogaz Ukrainy, Energorynok and Kyivstar.The Metro is expanding towards the city limits to meet growing demand, having three lines with a total length of 66.1 kilometres (41.1 miles) and 51 stations (some of which are renowned architectural landmarks).It connects the historic Uppertown, and the lower commercial neighborhood of Podil through the steep Saint Volodymyr Hill overseeing the Dnieper River.This service runs at standard 4- to 10-minute intervals throughout the day and follows a circular route around the city centre, which allows it to serve many of Kyiv's inner suburbs.But the trains are not reliable, as they may fall significantly behind schedule, may not be safe in terms of crime, and the elektrychka cars are poorly maintained and overcrowded in rush hours.