Princeton's main attractions cluster in two zones. The first is the university campus, anchored by Nassau Hall and centred on the chapel, the art museum, and a fine slice of American Gothic architecture you can wander through freely. The second is the battlefield and Institute area, a fifteen-minute walk south of town, where Washington's January 1777 victory and Einstein's twenty-year afterlife of equations both happened on the same square mile of farmland.
Add a stroll around Palmer Square and along Witherspoon Street, a coffee on Nassau Street, and the Albert Einstein House (still a private residence — view from the kerb only), and you have a full day. For more time, Drumthwacket and Morven each give an hour to the early Republic, and the campus's quieter corners — the Graduate College tower, the cemetery, the bulldog hidden on the chapel — reward unhurried wandering.