To Think Ash Lake is the very bottom of the map than Izalith
One thing I absolutely love about the interconnected world in this game in particular, isn't just the interconnectedness itself, but the sheer feeling of progressive
descent. You start the game in the brightly lit, sunny Burg. It's dilapidated and crumbling and swarming with hollows, but it's still pretty cheery by Souls standards. Then you go in the slightly darker and shaded lower Burg. Then you go in the gloomy, creepy Depths. Then the festering swamp of Blighttown. The further you descend, the more fucked up, creepy and hellish the landscape turns, with all the lava and demons and grotesque creatures (like the worms and centipede demon etc. ) and ruins of an epic ancient lost civilization, until you are in the very bowels of the Earth itself.
And then, underneath it all, is the most primordial place of them all, as said in the intro about the "Age of the Ancients":
a land of gray crags, arch trees, and everlasting dragons, manifested beautifully in Ash Lake.
I don't actually care about the lore and all that stuff, but the atmosphere and the
feel of progressively more intense
descent, the sheer sense of adventure taking you so deep into the most ancient primal layers of the Earth, expressed through exploration and gameplay, is just really, really cool.