A significant capital for 2,500 years – Merv was one of the most important oasis cities of the Silk Road and is among the major archaeological sites of Central Asia. It was declared a World Heritage Site in 1999. The second settlement of the site of ancient Merv is Gyaur Kala. Area 330 hectares.The Ben Makhan Mosque in the center is hardly recognizable. The Buddhist stupa and monastery in the southeast corner of Gyaur Kala are considered as the westernmost excavated example. Haroba Koshk-the ruins of the Nestorian church of the 7th century, are located 15 km from Old Merv, not far from the site of Dyue-Chakyn, this is a unique monument of Christian architecture, the only one revealed so far in Central Asia. The best remaining testimony to Seljuq power at Merv is the 38m-high Mausoleum of Sultan Sanjar.