Buried Haven / Forgotten Haven (new deep, underground biome concept)

The Buried Haven biome would be the opposite of the deep dark, as it would be decently illuminated and be more spacious/open. With a ceiling covered in an orange luminous crystal, flooring and walls covered with a variety of hardy plants (leafy bushes, ivy, or dragon fruit), and Goldspire Ginkgo trees (these would be a good addition because of the golden-colored leaves), this biome would add more reasons to venture and live deep beneath the ground. A new mob for this biome could be a large, hostile snake, possibly a constrictor, but aboveground animals like cows and chickens could spawn down here as well.

This rough concept is very open-ended, but the new livability of the Nether got me thinking about making the deepest depths of the Overworld more livable as well; deep dark being a fun challenge, and the Buried Haven being a safe, surfacelike sanctuary.