Cambridge, Massachusetts. The presence of MIT and Harvard is really only telling half the story. Places like Harvard Square and programs like the MIT Media Lab play a major factor in that ranking.
The bottom line is that the top engineering and biologist graduates from Harvard still want to date, party or at least meet interesting people. That just doesn’t happen if the area around even the most prestigious school isn’t happening.
Harvard Square is a mecca for nightlife, entertainment and art. Thus, it’s also a magnet for swarms of young people, many of whom are very attractive to the brightest minds coming out of the brightest schools who end up staying and starting the next Fortune 500s.