Thomas P. O'Neill Jr. Tunnel (Central Artery / Big Dig)

The Thomas P. O'Neill Jr. Tunnel carries I‑93 beneath downtown Boston as part of the Central Artery/Tunnel Project (the "Big Dig"). Much of the elevated Central Artery was placed underground by tunneling completed in the 1990s–2000s, and the Rose Kennedy Greenway was created on the former surface artery. The tunnel passes beneath City Hall Plaza and other central downtown locations, altering the city's surface streetscape.