A Vietnamese tour operator has seen an opportunity to promote Vietnam’s beautiful nature to the world when Hanoi is poised to host the second summit between leaders of the U.S. and North Korea next week. Oxalis Adventure Tours, which organizes commercial tours to Son Doong, has surprised Facebook users over the last few days with photos and videos of their exploring crew holding the national flags of the U.S., Vietnam and North Korea amid the remarkable natural beauty of the world’s largest cave. The photos and videos were all captured at the prominent discovery sites in the cave system in the north-central province of Quang Binh, according to Oxalis. The images of the national flags are symbol of peace, friendship and wishes for successful outcomes of the second summit between U.S. President Donald Trump and North Korean leader Kim Jong Un scheduled for on February 27-28 in Hanoi, the company said. These media products are meant to promote Vietnam’s tourism, according to Nguyen Chau A – owner and general director of Oxalis, taking advantage of the headline-grabbing event to capture attention of people around the world. A said that “each person, each agency has a different role in this historic…