摘要：The article is devoted the fortifications of the city Oster in the period between the 16th and 18th centuries. The Oster city has emerged as a border fortress in 11th century between the principality of Chernigov and principality of Pereyaslav’l. In the Late Middle Ages it was castle border between the Rzeczpospolita and Muscovy. During its history the city has twice changed its position. The fortifications were three transferred on different places. They are almost no traces today.
