Abhar (or Awhar; ) is a city in the Central District of Abhar County, Zanjan province, Iran, and serves as capital of the county. At the 2006 census, its population was 70,836 in 19,136 households. The following census in 2011 counted 87,396 people in 25,646 households. The latest census in 2016 showed a population of 99,285 people in 30,932 households. It has historically served as a place of importance due to lying right between the cities of Qazvin and Zanjan. Name "Abhar" is a combination of the words āb (water) and har (mill), due to the various water mills in the area. The locals refer to it as "Awhar". In the 10th-century geography book Hudud al-'Alam, the name is also spelt as "Awhar". Yaqut al-Hamawi (died 1229) likewise reports that the Persians called the city "Awhar". Foundation The Abhar-rud valley has remains and artifacts that date back to the 2nd millennium BC. Abhar's ancient origins are further demonstrated by the fact that it is linked by Islamic-era writers to mythological and semi-mythical individuals in Kayanian era. In his Tarikh-i guzida, Hamdallah Mustawfi (died after 1339/40) reports that the founder of Abhar was the Kayanian ruler, Dara II, whose historical counterpart is the Achaemenid ruler Darius III (). However, in his Nuzhat al-Qulub, Hamdallah Mustawfi credits Kay Khosrow with the city's foundation. Yaqut al-Hamawi attributes the foundation of Abhar and its fortress to the Sasanian ruler Shapur II (). Another fortress appears to have been erected or added on top of this old fortress at a later time. According to Hamdallah Mustawfi, Nushtagin Shirgir Saljuqi's descendant Baha al-Din Haydar constructed the Haydariyya castle on the location of a fortress. History Abhar has served as a vital spot since antiquity due to its location on the route that links Dinavar to Qazvin and Zanjan as well as the central areas of Iran to the region of Azerbaijan. It was conquered in 643 or 645 by al-Bara' ibn Azib during the Arab conquest of Iran. The inhabitants of Abhar initially put up a fierce fight which lasted for several days, but eventually sued for peace, which the Arabs agreed to. Abhar was part of the Jibal region, which would later in the 11th-12th centuries become known as Persian Iraq. Ibn Hawqal, writing in the 10th-century, reports that the inhabitants of Abhar were Kurds. The Samanid ruler Ismail Samani () captured Abhar during his