The Thomas P. "Tip" O'Neill, Jr. Tunnel is a highway tunnel built as part of the Big Dig in Boston, Massachusetts. It carries the Central Artery underneath downtown Boston, and is numbered as Interstate 93, U.S. Route 1, and Route 3. It roughly follows the route of the old elevated Central Artery, though the northbound entrance, at the corner of Kneeland St. and Atlantic Ave., is somewhat east of the southbound exit (at Kneeland and Albany St.) to allow for a reconfigured interchange with the Massachusetts Turnpike. It runs from the Zakim Bunker Hill Bridge at its north portal to Boston's Chinatown at its south portal.