Material testimonies of the Middle Ages on the territory of Sofia are relatively scarce, judging by the results of archaeological research carried out in recent years. However there is enough data from the written sources for the development and history of the city during this period.
The Bulgarian Khan Krum conquered Serdica in 809, but its final accession to the First Bulgarian Kingdom was during the reign of Khan Omurtag (814-831). The population becomes predominantly Slavic. At that time the new name of the city emerged - Sredets.
In the period of the XI-XII century Sredets is under Byzantine rule but it does not lose its significance. During the Second Bulgarian Kingdom (end of the XII-XIV century) the city thrives economically and culturally. In this time many monastery complexes are founded in its vicinity, so-called nowadays as Sofia "Minor" Mount Athos. In the last decades of the XIV century, as evidenced by the Vitosha charter of Tsar Ivan Shishman (1371-1395), the city began to be called Sofia, after the name of the basilica built around it, and in the XV century the new name is finally imposed .
In 1382 after a three-month siege Sofia fell under Ottoman rule and was included in the administrative system of the Ottoman Empire. The city is adapted to the needs of the new state and religious authorities. During this period the "St. Sofia" basilica was rebuilt in „Siaush Pasha”mosque. The traces of active life in this period are revealed in most of the archaeological excavations in the central parts of the city, just below the modern layers.
