This is the stuff of science fiction, from Peter Hamilton’s “Arcologies” on a future earth, and many other sci-fi stories… the ultimate super-rail project that beats airlines anyday! It would also qualify as one of the most audacious building projects humanity had ever undertaken, and may just be possible with the amazing TBM technology above.
Then, in the words of Fred Hapgood, the aim would be to:
The next step might be draw up plans for the ultimate TBM megaproject: the world subway. Maglev trains running through tunnels are the logical successor to air travel, at least between large cities. Unlike supersonic airplanes, trains in depressurized tunnels can run at many times the speed of sound without bothering residents with sonic booms or raising any of the land use issues that strangle airport development everywhere. Magnetic levitation means no rolling resistance and evacuated tunnels mean less air resistance. In a couple of decades we may see planners wrestling with the meaning of life in a society in which the major cities of the world are within a few hours’ commute of each other.
via Underground Space.