This is the 16695th most frequent Russian word.
скале
"Скале" is the dative or prepositional case of "скала," meaning "rock" or "cliff."
Here, 'скале' is a dative or prepositional form referring to 'rock' or 'cliff', indicating location.
На скале возвышалась старая крепость.
An old fortress towered on the rock.
In this sentence, 'скале' denotes the location where the eagle is situated, using it as a physical landmark.
Мы увидели орла, сидящего на скале.
We saw an eagle sitting on the rock.
Here, 'скале' personifies the rock, using it in the dative case to indicate what managed to withstand something.