Environmental requirements make it necessary to build underground transmission systems in special areas with special requirements. Limiting values for the use of overhead lines could be magnetic field restrictions, or just visibility of the overhead line, or limited space. The gas-insulated line (GLI) is one technical solution to allow the transmission of electricity under ground at high transmission ratings. The cost reduction of the second-generation GIL compared to the first generation, and the increased productivity in laying of GIL directly buried or in a tunnel, makes the GIL a high power rating underground transmission solution for the future.