Sentence:  She perceived what is one of Boston's chief charms,—that the Common and its surrounding streets make a natural centre and <WSD>rallying-point</WSD> for the whole city; as the heart is the centre of the body and keeps up a quick correspondence and regulates the life of all its extremities. 
Meaning of the word marked with <WSD> tags:  A cause, symbol, or a place that may unite a fragmented group or persons opposing each over in other matters.