The diagrams show the cross sections of two tunnels one joining France and Italy and the other joining two Japanese island

The diagrams describe two tunnels in terms of the cross-sections, one connecting France and Italy and the other connecting two islands in Japan.
Overall, while cross-sections of Mon is under the mountain, that of Selkan is under the sea. It is also clear that cross-section of Selkan Railway Tunnel is longer than that of Mont-Blanc.
It can be observed that while the cross-section of Mont Road tunnel is 11,7 km, that of Selkan Railway is much longer, at 42 km. The height from the former to the top of its mountain is 3km. This tunnel stretches in a line shape connection Italian End and French End together.
The cross-section of Selkan is 240m below the sea level bridging 2 islands which are Aomori city and Hokadate island. Two parts of this tunnel under 2 islands are higher in comparison to the rest lying below the ocean.