Dong Nai, Aug. 22 -- Deep in the teak forest in Phu Hoa commune, the southern province of Dong Nai, lies one of Southeast Asia's longest volcanic cave systems that has remained untapped despite its extraordinary significance. The discovery was made by explorers from the German Speleological Federation and experts from Vietnam's Institute of Tropical Biology, who surveyed a cave network in the Phu Hoa commune, which was formerly part of Tan Phu and Dinh Quan districts. Their findings revealed that Doi (bat) Cave stretches up to 534 metres, including collapsed sections, with its longest continuous passage measuring 426 metres. At its widest point, the cave reaches four metres high and ten metres wide. The La Nga Agricultural Seed Station ma...