Space

Yes, but again, you're just giving a bunch of vague "maybe" and "it's possible" aliens can't do this stuff without explaining specifically why it's not possible. We don't see any particularly insurmountable obstacles ahead of us for our civilization here in our solar system, why would it be different for all other civilizations?

I can indeed imagine humans for real building a settlement on Mars, especially given that there's no particular time limit - if your suspension of disbelief doesn't allow you to give it credibility in a century, how about giving us ten thousand years to do it? That doesn't change anything significant as far as the Fermi Paradox is concerned. Colonizing one planet every ten thousand years is still blindingly fast on a cosmic scale.