The computer software that is so essential to building the Louvre Abu Dhabi includes a virtual reconstruction, which shows all 85 of the supersized elements that will create the museum's dome.
As each of the huge steel frames is lowered into place, its equivalent part on the screen changes colour.
It was a December morning last year when the first of those pieces turned from red to green. Barely nine months later, the virtual dome has only a single red-lit piece remaining.
On a humid morning in the real world, it dangles just inches off the ground from a mobile crane parked a few metres from the canopy.
"This is good day for us," says Amer Kharbush, project manager for Turner Construction. "It makes the dome pretty much complete."
Today lacks the drama that came with installing the first supersized piece over two days of high tension that finally ended in success.
Few of the hundreds of workers on the site pay the final piece any attention. For them it is just another day on the job.
Yet this is a real landmark moment. The completion of the dome comes little more than a year before the museum is due to open. Once the final piece is in place, everyone will breathe a little easier.
At 9am, the chains holding the 67-tonne wedge of grey steel to the crane's hook take up the slack. The piece is the last part of the canopy's rim, a small chip from an otherwise perfect saucer.
Since the first piece was raised the pace has quickened, as the roof grew anti-clockwise with the assistance of a crane capable of lifting 1,600 tonnes, which needed its own road to support the weight.
By contrast, this final moment is anti-climactic despite the milestone it represents. The penultimate piece was in place only a day earlier.
This morning a much smaller 600-tonne capacity crane begins the lift almost unobserved. The steel part rises slowly as the crane boom swivels through 180 degrees to align it perfectly with the space it will fill.
It slowly drops into place, imperceptibly merging with the greater mass of the dome. Workers pull on trailing ropes to prevent unwanted lateral movement in the final stages.
The only real moment of drama comes as a huge superyacht flying the UAE flag cruises slowly past the scene. By the time it has reached the open sea, the lift is over.
The whole thing has taken barely half an hour.
"We still have a lot of work to go after the dome," says Mr Kharbush, "but it's one of those milestones that we can check off the list. It's done, it's out of the way, let's concentrate on the next task."
Since the installation of the final major element, which took place late last month but was only made public yesterday, most of the remaining beams that will connect the last of the supersized pieces have been bolted into place.
In the next few weeks, the completed dome will be jacked up, the temporary supports taken away and the entire canopy, with its circumference of 565.5 metres, will be lowered on to the four piers that will bear its 12,000 tonnes.
And after that?
"After that we start the cladding – four layers of cladding on the top and four on the bottom," says Mr Kharbush. "That is what makes the rain-of-light element, and that's the next big thing."
For those in charge of the Louvre Abu Dhabi project, placing the final supersized part represents an even bigger moment.
"It's pretty much a year to the date for job completion, so it's kind of significant because it marks the one-year countdown to finish the work," Mr Kharbush says.
After 286 days and 85 pieces, the computer simulation that tracks the progress of the dome is now showing nothing but green.
"It's looking good for next year."
jlangton@thenational.ae
The story of the Louvre Abu Dhabi’s final puzzle piece
Red turns to green on a computer screen, signifying completion of the museum’s dome and a major milestone in its construction. For the workforce it’s just another day – but not for Louvre watchers.
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