The Livingston-based firm will lead a £3 million second phase of redevelopment work, opening up the 19th century "birthplace of astronomy and timekeeping in Edinburgh" for public use, while adding a new restaurant and gallery space. Work is commencing this week.
The project, which will lead to the creation of a world-class hub for contemporary visual arts and important new work by local and international practitioners, will last about 11 months.
Simon Phillips, Esh's regional managing director for Scotland, said: "Historically, Calton Hill was a place for stargazing, but it will now house one of the finest visual arts spaces in the country as part of a wide-ranging attraction that will be open to all.
"It will encourage creative interaction, while still placing a firm onus on the site’s astronomical origins, not to mention showcasing wonderful views over Edinburgh to the Forth bridges. We believe that is a key project for the city, its inhabitants, and its many visitors, helping to further enhance the Edinburgh experience."
At the heart of the conservation project, the revitalised observatory complex – featuring a classical Greek-style design that was masterminded by William Henry Playfair in 1818 – is to become fully accessible to the public for the first time.
It is hoped that the project – commissioned by a partnership of Edinburgh City Council and visual arts body Collective – will encourage fresh engagement with, and creation of, the arts.