The rim of Colombo is circular, although slightly indented along the northwest where Colombo A intrudes slightly into the interior. The inner wall is asymmetrical, being much more narrow to the north and northwest and wider to the southeast. The rim is somewhat eroded, and several tiny craterlets lie along the inner wall to the southeast. The small satellite concentric crater [uk] Colombo B[1] lies across the south-southwestern rim.
Satellite craters
By convention these features are identified on lunar maps by placing the letter on the side of the crater midpoint that is closest to Colombo.
Menzel, D. H.; Minnaert, M.; Levin, B.; Dollfus, A.; Bell, B. (1971). "Report on Lunar Nomenclature by the Working Group of Commission 17 of the IAU". Space Science Reviews. 12 (2): 136–186. Bibcode:1971SSRv...12..136M. doi:10.1007/BF00171763. S2CID122125855.