CNN
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Monaco may be the second smallest country in the world, but it is also one of the richest. Almost a third of its residents are millionaires, lured to the French Riviera city state by its lenient fiscal policy – income tax was abolished in 1869. It is estimated that 70% of the population is foreign-born, while just 10,000 are locals, “the Monegasques.”

Construction has begun on Monaco's $2.3 billion offshore extension project to reclaim 15 acres of land from the sea.

Monaco is smaller than New York's Central Park and home to nearly 38,000 residents. Only 10,000 were born locally -- they are known as the Monegasques.

But the second smallest country in the world is running out of space. Since the early 19th century, Monaco has expanded an additional 100 acres into the sea, accounting for 20% of its total territory.

The planned extension will reclaim the equivalent of approximately 11 American football fields (15 acres) from the sea.

The new ambitious offshore extension project -- Portier Cove -- will house an additional 1,000 permanent residents in luxury apartments and villas.

Additional public spaces will include a hill and landscaped park, a seafront promenade and a little marina.

Private financers will front the $2.3 billion project and are expected to make over $4 billion from the sale of real estate, according to Urban Extension Project Director Jean-Luc Nguyen.

The extension will be protected by a seawall consisting of 18 concrete-filled chambers -- called caissons.

The foundation will be filled with quarried rocks and marine sand extracted from northern Sicily.

Prior to construction, protected plant species inhabiting the project area were relocated to nearby marine reserves. A wide variety of artificial habitats will be installed to compensate for the loss of natural habitats.

Once complete in 2025, the sun and sea will provide 40% of the district's energy needs, through the use of solar panels and pumps that use sea water to heat and cool buildings.

Elongated balconies will provide shade from the sun in summer and help recover heat in winter.

The district is designed to follow the curve of the coast so it does not obstruct marine currents.

The plan is to install a Mediterranean landscape of tall pines and other native vegetation in order to make the artificial extension feel more natural.