Modern cosmology is based on the cosmological principle – that the Universe is sufficiently homogeneous and isotropic, on large scales, to be described by a Friedmann-Lemaitre-Robertson-Walker (FLRW) model. On scales smaller than ~80 h^-1 Mpc, however, the Universe is inhomogeneous and anisotropic. Upcoming cosmological surveys are expected to reach a precision at which general relativistic nonlinearities could affect our observations. In order to precisely quantify the general relativistic effects associated with nonlinear structures, we must use numerical relativity. I will present our work involving a realistic cosmological simulation using Einstein’s general relativity, with a view towards quantifying the effects of nonlinear structures on observational cosmology.