In Eastern Massachusetts, Boston is located at the innermost point of Massachusetts Bay, at the mouth of the Charles River. The Charles River is longest river located entirely within Massachusetts, (although the Westfield River can be considered longer if one combines its upper and lower branches); however, the Connecticut River is the Commonwealth's—and New England's—longest, and most significant river. Most of the population of the Boston metropolitan area (approximately 4.4 million) lives outside of the city proper. The City of Boston itself is densely urban. Generally, Eastern Massachusetts, including and surrounding Boston, is densely populated. Boston's suburbs stretch as far west as the City of Worcester in Central Massachusetts.