A full environmental concept art spread of a crystalline underground city, massive cathedral-like cavern with towering geode spires filled with luminescent gems in impossible colors, ancient stone architecture built around living crystal formations, glowing underground river cutting through the city with bioluminescent algae, tiny figures of underground dwellers walking across delicate bridges, dramatic crystal backlighting with prismatic rainbow refractions, deep amethyst purple crystal blue phosphorescent green ancient stone gray and aurora teal color palette, Painterly digital art style, concept art for video game, wide establishing shot with vertical scale and underground civilization details