UNLABELLED: While it is widely accepted that the steel-concrete interface (SCI) plays an important role in governing the long-term durability of reinforced concrete structures, the understanding about the primary features of the SCI that influence corrosion degradation mechanisms has remained elusive. This lack of knowledge can be attributed to, firstly, the complex heterogeneous nature of the SCI, and secondly, the absence of established experimental techniques suitable for studying the relevant SCI features. Here, we use focused ion beam-scanning electron microscopy (FIB-SEM) nanotomography to obtain high-resolution 3D tomograms of the SCI. Five tomograms, spanning volumes ranging from 8000 to SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1617/s11527-025-02602-3.