Sir Robert McAlpine has commenced work on a £85 extension Edinburgh International Conference Centre, a project which is expected to create up to 250 construction jobs.
The two-year construction programme will add an extra 21,000 sq ft hallto the conference centre, plus 180,000 sq ft of office space.
Extensive excavation works will remove around 120,000 tonnes of material.
The main structure will be built from 3,300 tonnes of steelwork.
Andrew McAlpine, director at Sir Robert McAlpine, said: "We are delighted to return to this site that we know well as main contractor for the Scottish Widows Edinburgh One building next door and the nearby Standard Life offices.
"We look forward to delivering another landmark building to this important area of the city."