GEK Terna Holding Real Estate Construction is a large Greek conglomerate which is listed on the Athens Exchange. Its construction branch Terna is one of the leading enterprises of its sector in Greece. GEK Terna's electric utilities branch Terna Energy lately focused on the production and transmission of renewable energy. Through its subsidiary Heron S.A., it is also involved in the construction and operation of thermoelectric power generation fueled with natural gas as well as the supply of Electricity and Natural Gas to consumers. Terna Energy is listed separately on the Athens Exchange. Wikipedia