The tunnel originally served five closely spaced stations: Boylston, Park Street, Scollay Square, Adams Square, and Haymarket, with branches to the Public Garden portal and Pleasant Street incline south of Boylston.

Boylston and Park Street were built with rectangular stone headhouses designed by Edmund M. Wheelwright that did not aesthetically match the Common.

Unlike the interior decor, the headhouses were sharply criticized as "resembling mausoleums" and "pretentiously monumental".

[4] In 1963, the northern part of the tunnel was extensively altered during the construction of Government Center and a new Boston City Hall on what had been the neighborhood of Scollay Square.

Another section was rediscovered by a City Hall employee in 1983; a 150-foot (46 m) piece was renovated for use as records storage.

[8] However, there have been proposals for the disused tunnel to become part of a new streetcar line that would partly replace access to rapid transit for southern Metro Boston neighborhoods that lost rapid transit service in 1987 with the demolition of the Washington Street Elevated southern section of the Orange Line.

The portal has since been sealed up and covered by Elliot Norton Park, but the dead-ended tunnel to Boylston survives underground, for a possibility of future re-use (see above).