This is the 16006th most frequent Russian word.
псковского
"Of Pskov" (relating to the Russian city or region of Pskov).
Here, 'псковского' is used as a genitive singular to denote characteristics related to Pskov, a city.
Эта книга рассказывает о псковского происхождения героях.
This book tells about heroes of Pskovian origin.
In this sentence, 'псковского' refers to something belonging to Pskov (the Kremlin), indicating possession or association.
Я всегда хотел посетить псковского кремля.
I always wanted to visit the Kremlin of Pskov.
The term 'псковского' modifies 'искусства' to describe art associated with Pskov, showing an attributive relationship.