Erk-Kala was the center of ancient Merv. The fortifications of Erk-Kala have sagged under earth drifts but nevertheless, have preserved their height and power. This distinguishes Erk-Kala from other fortresses. Now the height of the fortifications with steep slopes and precisely cut out towers reaches 25 - 29 m.
The fortress area is about 20 hectares. The fortress used to have a massive circular structure without entrance at first sight. Actually, the only entrance there was located on a hill (from the southern side of the fortress). Inside the ancient settlement can be seen the remains of the ruler's palace. From the north there was the city square (intended for big masses of people). Erk-Kala was called Margush for some time.