Many people prefer living on the left bank of the Charles River in “Camberville” (i.e. Cambridge plus Somerville) rather than on the right bank of the Charles River in Boston. The left bank has a more liberal vibe, offers a different mix of amenities and it tends to be less expensive. It is also the center of the technology corridor that is forming along the Red Line as Tech industries and start-ups migrate into the city from the suburbs.
People tend to cross the river only to access the amenities that are not available locally and they tend to use the most convenient path (the Red Line).
For context, Somerville ranks 16th in the nation for population density (ahead of both San Francisco and Boston). It has a population of 76,000 and an area of 4 square miles. Cambridge ranks 26th for population density (just behind San Francisco, but ahead of Boston). It has a population of 105,000.and an area of 6.5 square miles. Somerville ranks second in the country for density of young people and artists, while Cambridge ranks third. As a result, there are lots of things for young people to do, all located in a very small area. Note that this does not include the populations of Tufts, Lesley, Harvard or MIT.
https://en.wikipedia.org/wiki/List_of_United_States_cities_by_population_density
For better or worse (depending on your interests), both Cambridge and Somerville are ranked among the top 20 hipster cities in America.
https://www.cbsnews.com/media/the-19-most-hipster-cities-in-america/15/
Somerville’s vibe has been compared to Brooklyn
https://www.boston.com/news/local-news/2015/07/30/sorry-but-people-in-somerville-dont-feel-like-theyre-in-brooklyn
Both cities were classic “streetcar suburbs” that grew up around the turn of the century and, as a result, they are organized around “squares”. The major squares in “Camberville” are listed below, in order of popularity.
For context, it is about two miles from Tufts to Harvard and about two miles from Harvard to MIT.
Davis Square (near Tufts, on Red Line)
Harvard Square (at Harvard on Red Line)
Inman Square (between Harvard and MIT, will be on Green Line Extension)
Central Square (between Harvard and MIT, on Red Line)
Union Square (near Harvard, will be on Green Line extension)
Porter Square (between Harvard and Tufts, on Red Line)
Kendall Square (at MIT on Red Line)
Teele Square (near Tufts) and
Ball Square (near Tufts, will be on Green Line extension)
http://archive.boston.com/yourtown/specials/square_face_off/
The top 6 squares are among the 17 most livable Boston neighborhoods. They are described in the article linked below. The bottom 2 are not really residential, but they are walk-able from Tufts.
https://www.thrillist.com/lifestyle/boston/what-boston-neighborhood-should-you-live-in
Powderhouse Square and the Medford Hillside abut the Tufts campus and Medford Square is walk-able.
A few more squares will be connected by the Green Line extension which will terminate on the Tufts campus near Medford Hillside. Here is a map:
http://greenlineextension.eot.state.ma.us/documents/about/ProposedMap/projectMap.pdf