This is the 12385th most frequent Polish word.
murów
"Murów" means "walls" or "masonry" in English.
The word "murów" here is used in the genitive plural to signify "of the walls", specifically referring to the walls of the castle.
Renowacja murów zamku była kosztowna.
The renovation of the castle's walls was expensive.
In this sentence, "murów" is also in the genitive plural form, indicating possession/association with the frescoes.
Podziwialiśmy freski na starych murów.
We admired the frescoes on the old walls.
The term "murów" here is in the genitive plural form, used after the preposition "między," demonstrating its role within the prepositional phrase.