Mass Ave is 16 miles long. Yeah, we didn't know that, either. For all intents and purposes, when we say "Mass Ave," we mean the portion of Mass Ave the Number 1 bus covers. An up-down on that route serves as a lazy introduction to Boston and Cambridge, with stops at the South End, Newbury Street, Central Square, and finally, Harvard Square. Once you've seen that, all you need to do to know the city is get dinner at Faneuil Hall and dodge vomit puddles in Allston.