Going to spend the winter near Belyov, Ulugh Muhammad built near the town a kind of fortification ("ostrog") – wicker walls were covered with snow and watered. After the water froze, a strong "ice fortress" was formed. The fortification was well located: from the West and South the approaches were protected by a deep ravine, along which the Belyovka River flowed, and from the East there was the steep bank of the Oka River.