The Fort McHenry Tunnel is a four-tube, bi-directional tunnel that carries traffic on Interstate 95 (I-95) underneath the Baltimore Harbor. The lowest point in the Interstate System under water, the tunnel is named for nearby Fort McHenry. The tunnel was constructed from May 1980 to November 1985, at a cost of about $750 million. At the time of its opening on November 23, 1985, it was the most expensive underwater tunnel project in the United States, but that figure has since been surpassed by the Big Dig project in Boston.