Four visualizations of the TNG-Cluster volume at z = 0. TNG-Cluster is a “virtual” simulation box constructed by stitching together the results of 352 individual zoom simulations. Each halo targeted for high-resolution simulation is marked by its Halo ID and a white circle demarcating 10r_vir. Top left: projected gas column density, showing high-resolution gas together with the first three intermediate (buffer) regions. Top right: FoF-scope gas of all halos (which exist only in high resolution regions), together with all outer fuzz of the first (most massive) zoom target, which evidences the gradual coarsening of resolution as we move away from the central re-simulated halos. Lower left: high-resolution dark matter particles. The visible areas of nonzero mass density therefore show exactly the high-resolution regions of the zooms. Lower right: parent, gravity-only volume of TNG-Cluster-Dark, from which massive halos were chosen for re-simulation. Shown in projected dark matter surface density, the large-scale structure is consistent with the three other views from the reconstructed, hydrodynamical TNG-Cluster volume.