"An Historical Atlas of Central Asia" written by Yuri Bregel. This is stated on Page no 83 of this book.

Samarqand is the most ancient city of Central Asia; the earliest archeological remains on the territory of the city belong to the 7th century B.C. The city first appears in historical records in the accounts of the campaigns of Alexander the Great (see map 3). Greek authors mention the name of the city as Marikana, which is, presumably, a Greek transcription of the original Sogdiana Samarkand. It was the capital of Sogdiana, and was reportedly
destroyed by Alexander, but then rebuilt. There is almost no information about the subsequent history of the city until the time of the Arab conquest (late 7th-early 8th centuries; see map 8), when it was the residence of a Sogdiana ruler with the title ikhshid. Samarqand was captured by Qutab Muslim in 712 and remained in the hands of the Arabs. In 819 the Samanid Nuh .
Assad became the governor of Samarqand, but later, under Ismail b. Ahmad, Bukhara became the capital of the Salmonids and Samarqand remained the second city, in importance, of Mavarannahr (see map 10). During the first centuries of Islam the city consisted of three parts: the citadel (khandvis), the town proper or inner city (shahristan, or madina), and the suburbs (rabad). The citadel and the shahristan were located on a hill on the southern bank of the Siyah-ab (now pronounced Siob), a major canal carrying water from the Zerafshan (“The River of Soghd”); but the main source of water for Samarqand was another canal, Dargham (pronounced Darghom), much farther south, from which secondary canals took water northward to the city.
The shahristan, together with the citadel, was surrounded by a wall and a deep moat. In order to supply water to the shahristan across the moat, an aqueduct covered with lead was built, probably in pre-Islamic times.
The suburbs were south of the shahristan. The suburbs located closest to the shahristan were also surrounded by a wall, which later became known as Divar-i Kundalang (lit. “Transverse wall”), and the entire oasis of Samarqand was surrounded by yet another wall popularly known as Divar-i Qiyamat (“The Wall of the Day of Judgement”).

Samarqand was destroyed in 1219 during the Mongol conquest. The Mongols also destroyed the aqueduct supplying water to the shahristan. The pre-Mongol city became known first as Hisar-i Qadim (“Old City”) and later as “Afrasiyab,” from the name of one of the main heroes of the Shahnama. In the next century city life gradually concentrated in the former suburbs, and Afrasiyab was abandoned. A new flourishing of the city took place under Timur, who made it his capital; he built new city walls with a citadel on the city’s western side, and embellished the city with some outstanding buildings and gardens (see below). Under the Abulkhayrids and the Ashtarkhanids Samarqand yielded its primacy in the state to Bukhara, which became the capital from 1557.
In the second and third quarters of the 18th century, during the internal feuds and general political turmoil under the last Ashtarkhanids and the first Manghïts, Samarqand suffered more than other cities of Mavarannahr, and, according to some sources, remained almost uninhabited. However, other sources indicate that the devastation to the city was not so complete and that probably more than half of its former population still remained there.
The city was restored to some extent by the Manghït amir Shah Murad, but it still did not reach its previous size and prosperity. The city was repopulated by various groups who resettled from other cities and from some rural areas of the Khanate of Bukhara, and even from outside of the khanate (thus, three new city quarters were formed by people who came from Tashkent).