Rostov the Great reached the peak of its power in 13 century, shortly before Mongol-Tartar invasion. But after that the city lost nearly all its previous political influence. However, Rostov was the seat of the metropolitan for several more centuries. Having a big influence and being in the center of ancient Christian cities metropolitan Iona decided to erect for himself a strong fortress with fortified defensive walls and towers.
The construction of the walls began in 1664. As Patriarch Nikon, Iona believed that such ambitious projects were a way to assert the power of patriarch and metropolitan.
By 17 century Rostov was surrounded by many other Russian cities and so had no military importance. As a result, the fortifications of the Rostov Kremlin were significantly reduced. But anyway the Rostov Kremlin is an important architectural monument of pre-Peter Russia.
And when you come to Rostov you must have a tour of the Rostov Kremlin. From its walls you can have beautiful views of all 7 cathedrals and churches of the Kremlin. You can also visit the churches of John the Evangelist, of Ascension and of Savior on the Seni and see their most beautiful paintings made by Yaroslavl masters.