The Demisia Tunnel is a tunnel that starts from the Mariana Trench and ends in Unknown.
It's depth is over 12km, and some believe that, the depth is also over 13km and more.
The Demisia Tunnel was discovered on a visit of the Mariana Trench in a submarine.
In the submarine there are about 15 people, 9 americans, 5 germans and 1 british.
When they arrived at the Mariana Trench, they discovered a hole and went there, they managed to approach 12km but then disappeared, some believe that the pressure there was so strong that the submarine got crushed, the map there is the depth they reached about 12.3km