The manse at 138 Brattle Street in Cambridge's Harvard Square has not traded since way back in July 1996, when it went for a mere $818,500. Think about it: That was the year that this fall's incoming Harvard freshmen were born. The 5-BR, 4.5-BA dating from 1930 just hit the sales market through Re/Max Destiny, offering its location "on one of the most prominent streets in the country" and a two-car garage. (Take your pick as to which is more valuable.) There are gardens and 4,812 square feet of living space over three floors as well as workout and media rooms. Yours this go-round for $4,200,000, which makes 138 Brattle the priciest listing in all of Cambridge.