Merv was a major Silk Road oasis and the capital of the Seljuk Empire.
The city developed beside the Murghab River in the Karakum region, where irrigation made intensive settlement possible in an otherwise arid landscape. Its position connected Iran, Central Asia, Afghanistan, and routes leading toward China.
Merv reached exceptional importance under the Seljuks in the 11th and 12th centuries. Sultan Sanjar made it his capital, and the city became a major center of administration, scholarship, and trade. Its medieval population was probably very large, although exact estimates remain uncertain.
Merv was not a single settlement but a sequence of urban sites, including ancient and medieval city areas. The ruins are part of the State Historical and Cultural Park “Ancient Merv,” a UNESCO World Heritage Site. It is sometimes confused with Nisa, another important ancient center in modern Turkmenistan, but Nisa was associated especially with the Parthian period.