This was a slightly silly essay that seems to essentially be more "places PG likes" than any sort of objective analysis...

Great cities certainly do have a vibe, but Cambridge (MA), although it's a very nice place to live and obviously has tons of smart people, is actually a pretty sleepy place in general; for all it's charms, it isn't a "great city." The "density of the unfamiliar" which I think tends to characterize great cities isn't really so evident in Cambridge (the presence of MIT / Harvard / etc does generate some of this, but universities tend to be somewhat closed societies).