The Great Mushroom Pillars

The Great Mushroom Pillars are eight awe-strikingly large structures that stretch from the surface of the Carbon Planet to it's core. There are five upon the equator, two on the poles, and one on the planet's point of axial tilt.

The Pillars were created by some ancient civilization. It has a thick smooth wall made of packed together mycelium. Inside of them is a large square shaped column, and attached to these columns are large square platforms that are terraformed to contain landmasses and oceans and such, along with spheres of light that acts as a sun and spins around the columns. Upon each platform, except for a few exceptions, a large population of a single animal species were placed and have since evolved to fill every niche available.