For immersive world-building, you can't go wrong with Attack on Titan. The layers of political intrigue and the mythology behind the Titans create a universe that feels both vast and deeply personal. The way the show unravels its lore over time keeps you hooked, especially when you start piecing together the backstories of characters like Eren and Historia.
Another great pick is Made in Abyss. The Abyss itself is a character within the story, with its mysterious layers and the unique creatures that inhabit it. The melancholy and beauty of its world, combined with the rich lore about the relics found within, make it incredibly captivating.
What kind of world-building are you most drawn to? Do you prefer a more fantasy setting like Made in Abyss, or something more sci-fi like Gundam?