the Menachite Complex from Halo Reach, is among the hardest -IMO- Forerunner constructs to imagine accurately, based on its description in the book, as this place literally makes no absolute sense. It's a giant chamber about 3 kilometers in diameter built deep inside Menachite mountainwith a dome that simulated an open sky, with a dozen moons and clouds that morphed into geometric shapes. The chamber was described to exhibit spatial distortions and optical illusions, which proved disorienting to anyone attempting to reach the central tier. Apart from the glowing crystal at its center, the exact purpose of the chamber is completely unknown.