The Istanbul municipality plans to build an underwater walkway for pedestrians that will straddle the European and Asian sides of Turkey's most populated city. The Hürriyet newspaper reported the first work for undersea drilling will start in March and the project is expected to be concluded in 2019, the last term of longtime Mayor Kadir Topbaş.

A two-floor tunnel between the Kabataş district on the European side and the Üsküdar district on the Asian side will host a walkway and a bicycle lane some 20 meters underwater as well as a regular road for vehicles.

Topbaş, who has served as the city's mayor since 2004, announced the project he referred to as his "magnum opus" last April and said people would be able to walk from Kabataş to Üsküdar "completely underwater."

Although the details of the project remain shrouded in mystery, media outlets have reported that the long distance between the two shores of the city will be covered by moving walkways in the tunnel.

Kabataş, the city's ferry hub, was shut down to maritime traffic in July for the renovation of docks and an underground tunnel to relieve heavy traffic on the coast line stretching the city's European side.

Ferries, three bridges and the Marmaray – an underwater rail system – were the only three options to take between the two sides of the crowded city of more than 14 million people until the opening of the Avrasya Tunnel on Dec.20. The Avrasya tunnel is the first underwater highway tunnel between two "continents" spanning the city.

An underwater tunnel for pedestrians sounds like a far-fetched idea for social media users although they admit they would use it if it offers an underwater view through transparent walls, or at least, screens on the walls.

Besides, the short distance – only 2 kilometers and on moving walkways – may persuade more people take the walkway instead of flocking the ferries.