The Phong Nha-Ke Bang Cave Center in central Vietnam officially opened a 400-meter zip line over the Chay River to the entrance of Toi (Dark) Cave.
Phong Nha-Ke Bang Tourism Center, which manages the world famous cave system in Quang Binh Province, has hired three local climbers to guide tourists.
Roughly 60 to 80 tourists per day have participated in trial runs of the service since August.
Most were foreigners.
Dark Cave (one of the oldest in the system) sits around 20 kilometers from Phong Nha Cave and was first explored by members of the British Cave Research Association in 1990 and 1992.
The cave is nearly 5.3 kilometers long and 80 meters high and was so-named due to its lack of sunlight and mysterious atmosphere.
Prospective zip-liners must climb to a high tower, where one can look down to see a large part of the Chay river and the jungle snaking between limestone mountains.
The staff helped us put on belts and harnesses.
I got to try the zip line along with two tourists from the US.
Seven other foreigners went before me, undaunted by a drizzle.
After landing on the dropping into the river on the other side, we took a boat to the cave's entrance.
Dark Cave isn't home to glittering stalactites and stalagmites like other caverns around Phong Nha, Tien Son or Thien Duong.
Its main attraction is a series of cool ponds one can swim in and several long, muddy grooves one can slide down.
There’s even a large hole in which to take a mud bath--in the dark, no less.
One the next ride, I and other tourists released ourselves into the river.