What thoughts and feelings are suggested by the choice of language to describe the landscape in the third, fourth and fifth stanzas?

And like to swan or moon the whole of Wales
Glided within the parish of my care:
I saw the green tide leap on Cardigan,
Your red yacht riding like a legend there,

And the great mountains, Dafydd and Llewelyn,
Plynlimmon, Cader Idris and Eryri
Threshing the darkness back from head and fin,
And also the small nameless mining valley

Whose slopes are scratched with streets and sprawling graves
Dark in the lap of firwoods and great boulders
Where you lay waiting, listening to the waves –

What area of country is covered?
What do the names evoke/represent?