Yerevan is the capital and largest city of Armenia, and one of the world's oldest continuously inhabited cities. Situated along the Hrazdan River, Yerevan is the administrative, cultural, and industrial center of the country. It has been the capital since 1918, the thirteenth in the history of Armenia, and the seventh located in or around the Ararat plain. The history of Yerevan dates back to the 8th century BC, with the founding of the fortress of Erebuni in 782 BC by king Argishti I at the western extreme of the Ararat plain. Erebuni was "designed as a great administrative and religious centre, a fully royal capital." Yerevan is home to dozens of museums, art galleries, and libraries. The most prominent of these are the National Gallery of Armenia, the History Museum of Armenia, the Cafesjian Museum of Art, the Matenadaran library of ancient manuscripts, and the Armenian Genocide museum. Others include the Modern Art Museum, the Children’s Picture Gallery, and the Martiros Saryan Museum. Moreover, many private galleries are in operation, with many more opening every year, featuring rotating exhibitions and sales. The Matenadaran is a library-museum regrouping 17,000 ancient manuscripts and several bibles from the Middle Ages. Its archives hold a rich collection of valuable ancient Armenian, Greek, Assyrian, Hebrew, Roman and Persian manuscripts. It is located on Mashtots Avenue at central Yerevan. The Yerevan Opera and Ballet Theatre consists of two concert halls: Aram Khatchaturian concert hall and the hall of the National Theatre of Opera and Ballet named after Alexander Spendiarian. The Komitas Chamber Music Hall is the home of chamber music in Armenia. Numerous places in Yerevan are attractive for tourists, such as the dancing fountains of the Republic Square, the State Opera House, the Cascade complex, the ruins of the Urartian city of Erebuni (Arin Berd), the historical site of Karmir Blur (Teishebaini), etc. The Armenia Marriott Hotel is situated in the heart of the city at Republic Square, while other major chains are also present in downtown Yerevan, such as the Royal Tulip Yerevan Hotel and the Best Western Congress Hotel. The Armenian Apostolic Christianity is the dominant religion in Armenia as well as Yerevan. The Armenian Church is represented in the city by the Araratian Patriarchal Diocese, with the Surp Sarkis Cathedral being the seat of the prelacy. Yerevan is home to the largest Armenian church in the world, the Cathedral of Saint Gregory the Illuminator, opened in 2001 when the entire Armenian nation had celebrated the 1700th anniversary of the establishment of the Armenian Church and the adoption of Christianity as a state religion in Armenia.