geofront

Japanese Wikipedia has an article on:

ジオフロント

Wikipedia ^ja

Blend of geo- +‎ waterfront

geofront (plural geofronts)

1. An underground urban area built to expand a city that is geographically limited.
   • 1996, International Journal of Offshore and Polar Engineering:

     Recently, intense interest has been shown in new frontier space development, such as waterfront and geofront, as underground space is called in Japan.

   • 1988, The Japanese Press, page 64:

     The tours covered a wide spectrum of subjects and places, including a geofront project, the Yokohama Exotic Showcase exposition, Sakaki town in Nagano.

   • 1990, Journal of Japanese Trade & Industry - Volumes 9-10, page 14:

     To achieve the role of one of the world's leading international cities by the beginning of the 21st century, Tokyo must move quickly to liberate its skyfront and waterfront areas to create more living and office space, improve its infrastructure by developing its subterranean geofront, and construct the facilities necessary for an international city, especially a 24-hour airport.

   • 1991, Advanced Robotics: The International Journal of the Robotics Society, page 430:

     However, as has been recently discussed as a topic in terms of geofront and waterfront developments, tunnelling of larger diameters and at greater depths is predicted to be necessary, so that the need for further automation and robotization is increased for the purpose of safety and improvement in productivity.

   • 2015, Maddy Koller, Star Maiden, page 81:

     I figured you two had probably seen something like that before, but I've never even heard of these geofronts existing.

At this point, geofronts only exist within Japan and in science fiction.