Erk Kala shows the first step in the process of urbanization in Merw. The smallest and earliest site, also known as Alexandria-Margiana, comprises 20 hectares and was enclosed by massive walls and a moat.

The only entrance-way had a ramp leading straight to the city. Archeologist Georgina Hermann described it as ‘One of the most imposing sites in Merw.’ The city’s wall was continually reinforced until the early Islamic period when both Erk and its extension Gyaur Kala were gradually abandoned.