Marmaray, linking European and Asian sides of Istanbul, has been opened on Tuesday with a ceremony.
Speaking at the inauguration ceremony of Marmaray, Gul said the Turkish government gave a great present to Istanbul and its people and on the 90th anniversary of the foundation of Republic of Turkey,
"We are proud of the project. The Marmaray is one of the biggest special projects for Istanbul as well as for the world," Gul said. " I believe that as long as the stability in our country continues, other great projects will be certainly presented to Turkish people."
Gul became the operator of the Marmaray on its first journey. Somali President Hasan Sheikh Mahmud, Turkish Parliament Speaker Cemil Cicek, Turkish Prime Minister Recep Tayyip Erdogan, Japanese Prime Minister Shinzo Abe, Romanian Prime Minister Victor Ponta accompanied Gul.
Marmaray started its first journey from Uskudar station on the Asian side at 17:19 Turkish local time an arrived in Yanikapi station on the European side at 17:39.
Marmaray will be free of charge for 15 days.
13.6-kilometer-long tunnel links Asian and European sides and it is 60 meters below the sea. It will take 4 minutes to cross from the European side to the Asian side.
The idea of the railway tunnel underneath the Bosphorus Strait was first introduced by Ottoman Sultan Abdulmedjid in 1860.
The rest of the Marmaray tunnel will be opened by 2015.
It will have the capacity to carry 75,000 people per hour in either direction.
