sentences:  The freeway runs north–south through Central New York, serving the cities of Binghamton, Syracuse, and Watertown.It passes through the Thousand Islands in its final miles and crosses two bridges, both part of the series of bridges known as the Thousand Islands Bridge.South of Watertown, I-81 closely parallels U.S. Route 11 (US 11), the main north–south highway in Central New York prior to the construction of I-81.