Nanoporous gold nanoparticles, so-called gold nanosponges, are characterized by their unique complex disordered inner morphology, leading to unique and interesting optical properties, for example strong enhancement of the electromagnetic fields and field localizations into spatially and spectrally well-separated sub-wavelength hotspots. However, theoretical investigations into these optical properties have been hampered by the quality of available geometry representations of the sponges’ chaotic nanometer-sized structure. We report accurate focused ion beam (FIB) tomography measurements of gold nanosponges with nanometer-scale resolution. Furthermore, based on these measurements, we develop a versatile algorithm based on the phase-field method that allows for the creation of equivalent disordered nanosponge geometries on the computer, avoiding the time-intensive experimental procedure. We carry out an in-depth analysis of both global and local geometric properties of the nanosponges, which characterize the complex structure of the nanosponge, and correlate these properties to their optical properties. We show that the computer-generated nanosponges agree in both global and local geometric properties as well as in the optical properties with the nanosponges experimentally measured using FIB tomography. Finally, we analyze anisotropies present within the experimentally measured nanosponges, for example due to substrate effects, and incorporate these into the phase-field based geometry creation algorithm. The resulting method is able to produce nanosponges with arbitrary anisotropies, which could be relevant for e.g., the catalytic properties of such sponges.