It is the only line on the LOCATION@1 , except for the two-station ORGANIZATION@1 line , which is operated entirely underground , with the only section of track to emerge above ground being the route to the depot from Seven Sisters to LOCATION@2 .

It is the only line on the LOCATION@1 , other than the two-stop ORGANIZATION@1 line , which is completely underground . The only section of track to come above ground is the route to the depot from Seven Sisters to LOCATION@2 .
