the tekkit pack includes the redpower mod, which includes sub-blocks. because some of use suffer the genetic disorder known as deutschen and require even more detail to obsess over.
what is that in the distance? see how it thrusts ominously into the white wimminz sky. and what is that speckling that dots the wastes around it? we approach to discover small patches of dirt amid the desert sands. the tower reveals little, save the barest glimmer of light from within. dawn's arrival gives us the strength to approach.
seeds? the small green balls deepen the mystery of the structure. we venture inside to find a strange pedestal surrounded by torches whilst water drips from the ceiling. our answers, it seems, lie upward. as we ascend, the level of detail increases and renewable energy systems creep into view. finally, the mystery revealed: the dark tower spooges water on to the desert to make the plants grow! it's not dark at all and we should accept it fully into our assholes hearts. like all big black cocks, the dark tower makes it rain.
tl;dr - check out this badass screenshot.