Aerial photography in 1958 revealed that during the Funan period a distributary of the Mekong entered the Gulf of Thailand in the vicinity of Ta Keo, which was then on the shore but since then become separated by some distance from the sea as a result of siltation. At that time, Ta Keo was connected by a canal with Oc Eo, allowing it access to the Gulf. The distributary of the Mekong revealed in the aerial photography was probably the "Saenus" mentioned in Ptolemy’s "Geography" as the western branch of the Mekong, which Ptolemy called the "Cottiaris". The Cattigara in Ptolemy's Geography could be derived from a Sanskrit word, either "Kottinagara" (Strong City) or "Kirtinagara" (Renowned City).