the original extension/run of the Orange line
the original North Station
abandoned tracks still visible, whether underground or aboveground
So, far, I've managed to find some photos, and know about the abandoned tracks visible from the Boylston T stop. I'm aware of the old entrance to Arlington in the Public Gardens (now filled in), and while I do know something about the 'A' line, I'm looking for more in depth, if possible. Also, a friend linked me this information via Wikipedia.
Any other information would be most helpful. Thank you.