The Seljuk regional capital, consisting of an ark (governmental quarters), a shakhristan (citadel) and a rabat (bazaar), considerably exceeded Damascus and Jerusalem in size and population.

Today the Seljuk citadel is called Sultan Kala. Adjacent to its two predecessors, and oval in shape, it occupies about 630 hectares. Its layout is still visible in aerial pictures. Among all city sites of Merw, perhaps the most significant is this medieval Seljuk city.