Available data concerning the 1600-year-old pillar in ancient Delhi, India is discussed. The pillar is of forge-welded wrought iron of average composition: C 0.15, P 0.25, S 0.005, Si 0.05, N 0.02, Mn 0.05, Cu 0.03, Ni 0.005%. While the composition of the material, particularly its low S and high P contents, is conducive to a low corrosion rate in the atmosphere, the deciding factor is the dry and unpolluted climate of the area, the large mass of the pillar being a contributory factor. That part of the pillar that is belo w ground is covered by a rust layer, about 1 cm thick, and shows deep pitting. Above ground, the pillar is coated by a protective oxide film,50-50 mu thick. Assuming a parabolic growth rate of the oxide film, its thickness is in accordance with the presentday corrosion rate of carbon steel at Delhi, determined by Hudson, and corresponds to the formation of an oxide film 5 mu thick in the first year. -- AATA