アブストラクト：
By targeting z~2-3 LBGs and quasars to faint magnitudes within a small area of the sky, it is possible to combine the Lyman-alpha forest absorption to give 3D maps of the absorption which traces the underlying large-scale structure. I will give an overview of our Keck observations targeting the COSMOS field, which yielded new insights into a known protocluster in that volume, and discuss theory work that suggests that large-volume observations with both Keck and Subaru-PFS will allow us to detect sheets and filaments of the cosmic web at these high redshifts.