Cambridge is served by the MBTA Red Line, which runs from Alewife in the west through Porter, Harvard, Central, Kendall/MIT, and Charles/MGH stations before crossing into Boston. This is the most useful transit line in the city — it connects all four main squares in a single 15-minute ride. The T runs frequently during daytime hours and less frequently late at night.
The city is highly walkable. Harvard Square to Central Square is a 20-minute walk along Massachusetts Avenue; Central Square to MIT is another 10 minutes. Cycling is practical and there is a Bluebikes bike-share system throughout Cambridge. Many visitors find that a combination of walking and the Red Line is all they need.
Driving in Cambridge is frustrating — parking is scarce, meters are aggressively enforced, and the streets around Harvard Square are congested. Leave the car at the hotel.