Take A Look Inside The World's First Intercontinental Subway Line [PHOTOS]

This week, Turkey opened the tunnel built to carry the world's first intercontinental subway line between the European and Asian sides of Istanbul.

The 8.5-mile tunnel, part of the larger "Marmaray" public transit project, runs 200 feet below the Bosporous, the strait that forms the barrier between the continents, according to The New York Times.

The goal is to reduce congestion caused by the millions of commuters crossing the strait using two road bridges and a network of ferries. Rides on the subway will be free for the first 15 days.

Critics are concerned that the tunnel is prone to flooding, does not have an electronic security system, and is in a seismically active areas, the Times reports.

Here are a few photos from opening day.

Japanese Prime Minister Shinzo Abe (R), Turkey's Prime Minister Tayyip Edogran (3rd R) and President of Somalia Hassan Sheikh Mohamud stand with Turkish President Abdullah Gul (seated) on the ceremonial first trip:

Looks like they enjoyed the ride:

An engineer performed a final check before the inaugural ride:

While others made sure the escalators in the station worked:

Meanwhile, the crowded ferries are still in use: