When the Islamic Arabs attacked the Sassanid empire in 634 CE, many Kurds resisted their invasion, but were eventually brought under Muslim rule. In 835 CE, one of the Kurdish leaders revolted against Al-Mu'tasim, but was eventually suppressed. The Kurds revolted against the Arab Caliphs several times but were defeated.
During the next few hundred years, Kurdistan became the arena of conflict between various invaders, including the Mongols and Timurids. Its steady decline began in the 16th century, when sea traffic replaced the famous Silk Road.
Upon the order of Sultan Muhammad Khodabandeh (Öljaitü), a small town by the name of Soltanabad Chamchal was constructed in Bisutun region to function as the official and political center of Kurdistan in the Middle Ages. It remained the capital for nearly one-and-a-half centuries, until, in 1372 CE, the government moved to Hassanabad fort, 6 km south of Sanandaj (Sinne). Around 14th century, people from Ardalan tribe established themselves in Sinne (Sanandaj) as the rulers of this region.
According to Sharafnama written by Sharaf-al-Din Bitlisi, the earliest known leader of the tribe, Bawa Ardalan, was a descendant of "Ahmad b. Marwan", who ruled in Diyarbakır. He settled down among the Gorans in Kurdistan and toward the end of the Mongol period took over the "Şare Zor" (Sharazur) region, where he established himself as an absolute ruler. He is considered to be the founder of the Ardalan principality. The territories of Zardiawa (Karadagh), Khanaqin, Kirkuk, and Kifri, which were already the homelands of the Goran-Kurds, all belonged to this principality. The capital city of the principality was first in Sharazour, but was moved to Sinne later on. During the reign of Shah Ismail I, the founder of Safavid dynasty, Sunni Kurds (among them the Ardalans) were supported by Ottoman Caliphs against the Shi'ite government of the Safavids. When Soleiman Khan Ardalan came to power in 1630 CE, the throne was transferred to Sanandaj (Sinne), and, from then on, the rulers contributed to the flourishing and development of the area.
Zarrinehorood, 302 km long, is one of the longest rivers of this province. Its banks offer great opportunities for recreation and the river's plentiful water renders itself ideal for water sports. This river runs northwards and ultimately pours into Lake Urmia. Sirvan river is another prominent river in this province. It runs over a long distance, eventually to join the Tigris in Iraq. The banks of this river are remarkably attractive. Zarineh Rood and Simineh rood are two other important rivers in this province. A large number of marine species and birds live on the banks of the province's numerous rivers which they seem to find ideal habitats.
Lake Zarivar is the most beautiful water-way of the province, which lies at the feet to high mountains, providing a delightfully picturesque sight. Its water is sparkingly fresh. The lake has a maximum depth of 50 m and an average depth of 3 m. It is surrounded by thick forests. The whole collection of the lake, the mountains and forests generates a fascinating panorama. This lake, which has a length of 5 km and a maximum which width of 1.7 km, lies to the west of Marivan. Lake Vahdat's dam, to the north of Sanandaj (Sinne), provides excellent opportunities for fishing and water-sports.
Kurdistan benefits from many resourceful mineral water springs. The most outstanding of these are: Govaz to the northwest of Kamyaran, Abetalkh close to Bijar and Baba Gorgor to the north of Ghorveh.
Cave Kereftoo, close to Divandarreh, is a unique natural and at the same time archeological site. Inside the cave there are a number of ancient buildings known as the Temple of Heraclius, because the name of this Greek god is carved on the ceiling of one of the halls. Cave Shoovi, 267 m long, is another prominent cave, which lies near the city of Baneh.
Mount Charkhaln 3,330 m high, mount Chehelcheshmeh, 3,173 m, Mount Hossein Bak, 3,091 m, and Mount Masjede Mirza, 3,059 m, are the other large mountains of Kurdistan.
Kurdistan has vast forests and refuges, where many animals and birds live, safely from the harms of the human beings: the leopard, ram, wild goat, hyena, jackal, wolf, fox, sable, wesel and such birds as the partridge, wild duck, stork, parrot and eagle.
The Kurdish language is categorized under the Indo-European group of languages, with a distinctive grammatical form. This language has various branches in Iran, such as the Sorani, Hewrami, Feyli, Kalhuri and Kurmanji. Majority of the people in Kurdistan province speak variants of Sorani Kurdish, sometimes called as "Ardalani" dialect. Hewrami Kurdish is also spoken around Marivan, in a region called "Hewramanî Text"(The Flat Hawraman). Eastern parts of the province including Bijar and Qorveh are inhabitated by Azeris who speak Azeri.