Cambridge geography has always been a bit mystifying. The Charles River should be your natural point of orientation. But it meanders all over the place; it flows North to South, then East to West.

But Cambridge is a city of Squares. Any place two or more streets come together, the City Fathers may proclaim a Square. And they rename them all the time. A few of the Squares-besides Harvard Square-are worth knowing.

Central Square: one stop on the MBTA or straight down Massachusetts Ave, on foot or by bus or car. This is the location of the main Post Office, City Hall, and the city's major business district.

Kendall Square: two stops on the MBTA. Located in the Eastern section of the city near M. I. T., Kendall Square is the site of a new $60 million NASA research laboratory. The laboratory will cover some 29 acres, and is expected to stimulate major new investment in the area.

Porter Square: about a fifteen minute walk north on Massachusetts Ave. from Harvard Square, Porter Square is the major business district for North Cambridge. The MBTA plans to extend its rapid transit to Porter Square (Harvard Square is now the end of the line) but lack of funds has held up the extension.