Maybe this is old news, but I just noticed today that google maps now has walking directions! They did not import properly into the embeddable frame though, but heres a screen shot and a link.
It knows that you can walk through Boston Common, and it knows where the paths are so you don’t just cut across the grass like a hillbilly. It also takes the esplanade and some of the paths near MIT. It did not, however, take the bike path near my house, there’s no faint line for it either, so that does make some sense. They do warn that it is in beta and that one should “use caution when walking in unfamiliar areas.”