Introduction to lava tunnels: Lava tunnels are also called "underground lava rivers". There are a large number of collapsed lava caves distributed on more than 200 square kilometers of lava moss. At present, nine cave entrances and five larger lava tunnels have been surveyed. The lava cave entrances are filled with purple mist. The cave is cold, deep and mysterious, and the landscape is strange. It is like a glazed palace, solemn and fascinating.