The fortress on Ishim had the shape of a regular hexagon with an area of about 2 hectares. At the corners of its equal distance located the bastions connected by curtain walls. The bastions facing the river were called Nagorny and Ishim. The total length of the fortress fence was more than 1.3 km. In the bastions were placed guns, inside the fortress-barracks, stables, officers ' houses, garrison Church, powder magazine, and other premises. Hard work exhausted the soldiers and Cossacks, as well as poor nutrition and early cold weather. People got sick, many died, and escapes became more frequent.