(Thanh Nien new, Monday, April 21, 2014) A helicopter tour around the world-famous Phong Nha – Ke Bang National Park in the north-central province of Quang Binh will begin operating at the end of this month. Three trips for 60 tourists will depart on April 26 or 27, Saigon Tiep Thi (Saigon Marketing) newspaper quoted the tour operator, Oxalis Adventure Tours Company, as saying. The company said the helicopter will fly around the 85,700 hectare (211,769-acre) park before flying over the Garden of Edam – a jungle housed inside Son Doong, the world's largest cave. The helicopter will also alight at the entrance of En (Swift) Cave, so tourists can explore the cave which goes 1,645 meters back into a mountain. According to Oxalis, En cave is a feeder to Son Doong and was once named one of the most captivating caves on earth by National Geographic . A half-day tour costs VND3 million (US$140) per tourist, while...