The underground IN-BETWEEN METROPOLIS is a downward expansion and a densification in the place of horizontal sprawl in order to prevent mobility and transportation growth issues of contemporary cities and metropolises. It is applied in three different cities: Mexico City, Berlin and Tokyo that identify three very distinct versions of city structure and urban growth in reference to the issue of mobility and transportation.
The vertical mega-structure involves: a ground surface that has DEPTH, a thick ground surface, a three dimensional crust of public spaces that will fill-in the gap, (the solid [under]ground between the surface and the underground transport infrastructure), a porous permeable ground, permeable by light, sounds and smells, where temperature will remain more or less stable all year round, where rain will no longer be a burden.
The in-between metropolis has a maximum horizontal dimension that can be walked within a reasonable amount of time. It can welcome the passengers of all transport means, including the private car or bike. It minimizes energy losses, thermal insulation needs and gas emissions. Waste of all kinds is treated locally or recycled. Particularities of location, climate, culture, soil conditions, underground water, available energy sources etc. will define the exact form of the in-between metropolis.