I mean, practically? Orion’s Arm.

Taking care of humanity is literally trivial.

There’s a big soup of civilizations and frontiers and mysteries to explore. Some danger to keep it interesting. Infinite and transcendental pleasure to experience, entire simulated worlds you can try.

But it’s grounded in real physics, so you don’t get that big can of worms from living in a universe that isn’t… self-consistent.

In other words, its as sci-fi as you can possibly get without things getting timey wimey.

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But my adventure-yearning-heart says Avatar.

Bending is just so freaking cool. It’s the best magic system ever.