Tiny, densely populated Monaco plans to push back the sea to make way for luxury apartment blocks and businesses.
The wealthy principality in the south of France has invited bids for the six-hectare (14-acre) development project.
The competing bids will have to be submitted by 23 July, and the plan is to complete the new district by 2024.
Reclaiming the area from the sea is expected to cost 1bn euros (£842m). The rocky tax haven has hardly any space onshore for new construction.
A similar project was abandoned in 2008 because of environmental concerns and the global financial crisis.
This time there will be a thorough environmental impact assessment, as the new site lies between two protected marine conservation areas. The new development will be near Grimaldi Forum, site of a seaside concert hall and huge conference centre.
The Monaco government says the new district will have to meet the highest environmental standards. Sustainable urban design will be a feature - so for example there will be access for vehicles, but the district will favour pedestrians and cyclists.
The apartment blocks will be from six to 10 storeys high and have private gardens.
The bid winner will have to manage the project finance, infrastructure and leasing of property.