In a ruling made public on Friday, Greece's Council of State effectively lifted the final barrier to a major investment at the site of the capital's old airport at Elliniko.
The decision of the country's highest administrative court deemed as legal the procedures that have been followed to date as regards feasibility studies and environmental issues.
Its reasoning referred to the fact that the plan foresees the drafting of additional environmental studies to accompany the progress of the project.
The decision followed another one last year that had deemed a comprehensive plan for the development of the site into as legal.
On Wednesday, Greek real estate company Lamda Development that it would be fully undertaking "the visionary Elliniko project" after talks with its foreign partners did not yield an agreement.
The company said it is ready to start work on the largest urban development project in Europe, which will have significant impact in the Greek economy, entrepreneurship and local communities.
The project is expected to create thousands of jobs and one of the largest parks in the world.