i dont think i know any other sources than google on this matter.
you can search like potala pure land, potala pure realm, avalokitesvara and potala and similar keywords. im sure you come up with something.
as to answer is it a symbolic place. i dont know, but i believe and and know that Avalokitesvara's pure land potala and potala mountain are real places, just like sukhavati.
If the thought of demons
Never rises in your mind,
You need not fear the demon hosts around you.
It is most important to tame your mind within....
In so far as the Ultimate, or the true nature of being is concerned,
there are neither buddhas or demons.
He who frees himself from fear and hope, evil and virtue,
will realize the insubstantial and groundless nature of confusion.
Samsara will then appear as the mahamudra itself….