Figure 4: The ancient cities of Merv. The earliest, Erk Kala, was founded c. 500 BC. Around 280 BC it became the citadel for the much larger Hellenistic city of Antiochia Marginana (today known as Gyaur Kala). Around the 8th century AD a new Islamic city of Sultan Kala was built to the west, although Gyaur Kala continued in use alongside this, becoming an industrial suburb. In the 15th century the Timurid city of Abdullah Khan Kala was constructed to the south, to which was added a suburb, Bairam Ali Khan Kala, around the 18th century. (Background IKONOS satellite image).