On June 25 , 2004 , the Causeway Street Elevated was permanently closed . After a weekend of substitute bus service north of Government Center , Green Line service to the underground North Station " superstation " began on June 28 . During the 2004 Democratic National Convention from July 24 to July 29 , 2004 , the disused Elevated was used as a platform for security personnel . After a year of substitute bus service while the new portal and incline connecting the tunnel to the Lechmere Viaduct were finished , regular service to Lechmere resumed on November 12 , 2005 . The replacement of the Causeway Street Elevated cost $ 310 million in 2005 dollars
2004 Democratic National Convention
2004 Democratic National Convention
Causeway Street Elevated