Before revision: Tunnel in Col du Galibier, France Tunnel in Fort de Mutzig, France Decorated portal to a road tunnel in Guanajuato, Mexico Utility tunnel for heating pipes between Rigshospitalet and Amagerværket in Copenhagen, Denmark Tunnel on the Taipei Metro in Taiwan Southern portal of the Chirk canal tunnel, Wales A tunnel is an underground or undersea passageway .
After revision: Tunnel in Col du Galibier, France Tunnel in Fort de Mutzig, France Decorated portal to a road tunnel in Guanajuato, Mexico Utility tunnel for heating pipes between Rigshospitalet and Amagerværket in Copenhagen, Denmark Tunnel on the Taipei Metro in Taiwan Southern portal of the Chirk canal tunnel, Wales Tunnels are underground constructions used for transportations .