Sunbeams shine down from the first doline in Hang Son Doong—the world's largest cave—located in Phong Nha-Ke Bang National Park, Quang Binh Province, Vietnam. I have been absent for the last two birthdays of my daughter, have journeyed 3 times into the world's largest cave and went through the usual trekking route of about 1.5 days in some four hours, and waited for this moment.