Turkish President Recep Tayyip Erdogan said the work of the technical study - the project of a tunnel of three floors unparalleled in the world - has begun.
Erdogan made the remarks at a rally of the ruling Justice and Development Party (AKP) in Istanbul's Asniurt district on Tuesday.
The tunnel, which will allow 75,000 passengers to cross the railway line, will be allowed at one hour.
Erdogan said that the roads dedicated to cars inside the tunnel allow the crossing of 120 thousand cars per day.
He stressed that the project will be implemented through cooperation with the private sector, and the President pointed out that the work of the technical study will end during the current year.
The Istanbul Grand Tunnel project consists of three floors, one dedicated to a train, and is planned to pass under the seabed in the Bosphorus Strait in Istanbul.
In another speech in Istanbul's Qasim Pasha district, Erdogan noted that Turkey was among the most polarized countries to own real estate in the world.
He said that his country had witnessed the sale of 35 billion dollars worth of property to foreigners during the periods of the governments of the Justice and Development Party, that is, since 2002.
Turkey's construction and housing sector, according to Erdogan, has a high profile in the country.