Introduction
Although large natural caves -mainly formed by karstification processes in carbonate rocks like limestone and dolomite - are known from Central and North Vietnam the limestone occurrences in the extreme south-west of Vietnam have never been subject to systematic speleological exploration and documentation. Only very few international speleological publications are available and the articles of Deharveng et al. (1995a, 1995b) appears to be the result of the only (biospeleological) investigations in this area so far.
However, the isolated small limestone hills of the Ba Hon/Ha Tien area are of great economic and environmental relevance (e.g. Kien Kuong Biodiversity Study, Executive Summary 2002), due to their importance for cement production as well as for their touristic significance. Indeed, a short search on the Internet immediately reveals the wealth of natural beauty of the area, called the "Ha Long of the South". Some caves are already now used as tourist attractions (e.g. Mo So cave, Hang Tien/Dong Dinh Cave, Gia Long Cave). 
The scenic limestone hills as well as the caves located therein, provide the basis for a strongly growing tourist industry in the region. In addition, these karst hills and their caves are developed along the coastline with its beaches, which underlines their value for tourism.
Due to the limited extent of the existing limestone hills it was not expected to find caves of great size. However, the karstification was, as expected, in a mature state. Many caves of great beauty were expected to have been found which would be suitable for a sustainable use for tourism. Consequently, a speleological surveying project was carried out in order to investigate the cave potential of the area in question and to document as many caves as possible.
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