Strange area in Demonis - how to get there?

[Karlos]

Hey guys, I saw this unexplored area in Demonis when I climbed the volcano (where you toss the hourglass), with some shops and stuff but never was able to get there. First I thought it opens later on but now I've finished the game and realized I never accessed that region.

It's sort of "behind" the portal to the golden dragon casino, on the other side of the mountain range. Was I just stupid or is it a bug?