I would fully explain in detail on how I use to practically live as that tree.. But it's way uber late and I'll just settle for maybe a small paragraph before my brain implodes.

First i must explain that the city sits around a small star, and resonates to that vibrancy, using what energy is given off from the star to rebuild, run, cunstruct, and basically "power" it.

Then we come to the secluded area just outside the city where a select part of space is cut off by all, with an atmosphere and everything! I lived out here..

Oh, um. So put simply, the cosmic tree sits on one of the smallest formations of collected crystals.. Meaning just a whole bunch of chipped, "imperfect," or otherwise unused crystals beings have donated upon creation of the city. They're reused as a life source for the tree[and stabalize the created atmosphere], which by the way, is actually every species of sprout, seedling, or being of plant-based life in one. There's not one like it that I know of.
I'm geting off-topic. Well, you can visibly see other places in the universe, as well as other planes of existance. Think of it as a Multi-dimentional Telescope with You as the Universal controler.
So, I think that's all I can give at this point. I'm gonna be busy the next few days~

Art © me.