Abstract: A transformer station for high and medium voltages is installed beneath the earth's surface, with at least one access point to the switchgear assembly and the ventilation shafts being arranged above ground. The station includes at least one power transformer for converting high voltage to medium voltage, at least one medium-voltage switchgear assembly and auxiliary and secondary as well as protection and control devices, and at least one access or transport shaft configured for transporting all large equipment and operating means into the station and can be used as an exhaust air shaft. The access or transport shaft has ventilation channels and a movable closure element. A base surface for placing the operating means and power transformers is provided beneath the access shaft. The power transformers can be inserted into boxes, which may be adjacent to one another, once the power transformers have been placed on the base surface.