Seeing the screenshots, I'm a little underwhelmed. When I imagine an underground zone, I was thinking of a tall, multilayered world like Azjol Nerub, or the Bionis interior from Xenoblade 1, or Draconis Mons from GW2, or the Hidden World from HTTYD3. What I'm seeing of Zaralek Cavern looks very flat, which isn't as majestic.
Draconis Mons from GW2, bottom layer
Draconis Mons 2nd layer
Draconis Mons 3rd layer
Xenoblade 1 Bionis interior
HTTYD3 Hidden World concept art
HTTYD3 Hidden World CGI environment
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Which is a shame, because they have made good looking underground expanses before, such as in the Nerubian dungeons in Wrath, or that vista at the end of Mechagon.