Erk-Kala was the center of ancient Merv. The fortress walls of Erk-Kala have somewhat sagged under the earthen deposits, but still retain their height and power. This makes Erk-Kala stand out from other fortresses. Currently, the height of the fortress walls with steep slopes and clearly carved towers reaches 25 - 29 m. The area of the fortress is about 20 hectares. The fortress was a massive round structure, at first glance without an entrance. In fact, the only entrance here was located on a hill (on the southern side of the fortress). Inside the settlement, the remains of the ruler's palace rise. On the northern part of Erk-Kala there was a city square (intended for the gathering of large masses of people). It was Erk-Kala that once received the name of the city of Margush.