Occurrence of Attributes in Original Text

The text related to the cultural heritage 'Historic and Architectural Complex of the Kazan Kremlin' has mentioned 'Fortress' in the following places:
Occurrence Sentence Text Source
In the 12th century, a white stone fortress was constructed, and the city became an outpost on the northern border of Volga Bulgaria.
The Kremlin, which in many respects kept the planning of an ancient Tatar fortress and which became an important centre of pilgrimage, consists of an outstanding group of historic buildings dating from the 16th to the 19th centuries, integrating remains of earlier structures of the 10th to the 16th centuries.
The Kazan Kremlin is the last extant Tatar fortress with traces of its original town-planning conception in Russia.
Criterion (iii): The historic citadel represents an exceptional testimony of the Khanate period and is the only surviving Tartar fortress with traces of the original town-planning conception.