Photographers and bystanders gathered on the banks of the bay and up on nearby lookout points to catch a glimpse of a project set to make life easier for Stockholm commuters.
IN PICTURES: Watch as the final segment is lowered and head into the tunnel
Citybanan, or the city line, has been designed to redirect commuter train traffic from the congested central station by adding a new station below the existing central metro site.
Trains coming in from the northern suburbs will first stop at a new station at Odenplan, continuing to the new central station and from there to southern Stockholm.
RELATED STORY: Five facts about the new Citybanan train line
The idea is to free up the existing central station for national rail services as well as freight services.
City planners hope the new commuter train tracks will be in use by 2017.
But that's enough reading - put on your hard hat and check out these pictures of the lowering of the final section and the progress underground so far on a glorious summer day.
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