On a budget, Isabella Stewart Gardner Museum still earns its price.
~$20; free if your name is Isabella
The most atmospheric museum in the city — the courtyard alone is worth the ticket, and the founder's will freezes the arrangement in time, including empty frames from the unsolved 1990 heist. The catch: it's small, the dim period lighting and no-labels philosophy frustrate some, and the famous stolen masterpieces are not there.