China is planning the world’s longest undersea tunnel (76 miles long) that will run between the cities of Dalian and Yantai.¬† Engineers will attempt to bore three tunnels¬†100 feet below the sea bed; one for cars, one for trains and one for maintenance purposes .¬† Design and construction of the tunnel will be a challenge since its proposed location is in area prone to earthquakes, as it passes through two major fault lines.