Situated on the eastern edge of a large fertile oasis watered by the Murghab River, Merv was historically an important departure point for travel across the 180km desert to Amul, part of the 'Silk Road' trade route. Today, modern Merv is known as Mary, an administrative center located 30km west of Old Merv. The ruins of Old Merv are located near the small town of Bairam Ali, a Russian garrison town established in the early twentieth century. The ruins of Merv are comprised of five walled cities dating from the sixth-century BC to the eighteenth-century: Erk Kala, Gyaur Kala, Sultan Kala, Abdullah Khan Kala and Bairam Ali Khan Kala. Grouped into three settlements corresponding to three periods, Ancient, Medieval and post-Medieval Merv, the development of these cities is unusual in Western Asia: instead of rebuilding upon the same site in successive layers, each city was abandoned for a new site nearby. Ancient Merv consists of the ruins known as Erk Kala and Gyaur Kala. Erk Kala, meaning citadel castle, was established in the Achaemenid period, sixth century BC, its massive enclosure maintained and reinforced until the early Islamic period. The Seleucid ruler, Antiochus I (281-261) founded the Hellenistic city Antiochia Magiana, the ruins now known as Gyaur Kala, maintaining Erk Kala as its citadel. The Gyaur Kala, occupied for over a thousand years under the consecutive reigns of the Parthians, Sasanians, and Umayyads, constitutes the longest living of the Merv settlements. Sometime before the eighth century, suburbs arose near the Majan canal, outside the fortified city. When Abbasid Abu Muslim established dynastic power in Merv in February 748 he relocated the government and major bazaars from the ancient city to a location near the suburb. Merv prospered at this site under the Abbasids and Tahirids, but went through a period of decline when political power moved to Nishapur and Bukhara. The Seljuks arrived in the eleventh century and revived the city, establishing it as an eastern Seljuk capital. Fortification walls were built to enclose the settlement at the end of the eleventh century, possibly by Sultan Malikshah (1072-92). Sultan Sanjar (1118-57) is credited with construction of a fortified citadel, the Shahriyar Ark, in the northeast corner, and the two walled suburbs that extend the city to the north and south. In three consecutive invasions of 1221-2 the Mongols sacked the medieval city of Merv, the ruins now known as Sultan Kala. The city remained occupied, but in an impoverished state until the Timurids integrated the area into their empire in the late fourteenth century. Shahrukh (1405-47) considered locating his capital here and founded a new settlement, now known as the Abdullah Khan Kala, a kilometer south of Sultan Kala. He instituted a major building program, rebuilt the irrigation system, and is credited with construction of the dam. Construction came to a halt however when Shah Rukh relocated to Samarkand, and Merv did not develop again until the Shaybanis reign (1500-98) under whom the fortification walls were erected. In the post-medieval period Merv remained a provincial center, a small town of less than a square kilometer boasting, however, one of the strongest fortresses of the time. A rectangular extension known as Bairam Ali Khan Kala was constructed to the west of Abdullah Khan Kala in the eighteenth century. These two sites were probably in use until the early nineteenth century. No longer occupied by the time of the Russian's arrival in 1885, many of the buildings had been dismantled to provide bricks for new construction. Sources: Herrmann, Georgina. 1999. Monuments of Merv: Traditional Buildings of the Karakum. London: The Society of Antiquaries of London. Nikitin, A. B. and Zeymal, YE. V. 'Merv'. Dictionary of Art vol. 21, 167. "Merv". World Monuments Fund Panographies. http://www.world-heritage-tour.org/asia/tm/merv/map.html. [Accessed February 2, 2006]