Culturally, the Delaware Valley is taken by various commercial media and advertising venues to mean the Philadelphia metropolitan area, but geographically, geologically, and historically the term used to refer to the valley through which the Delaware River flows. In geology and geography, a strict sense of the term would incorporate the Delaware River's main drainage basin, so encompass major tributaries such as the Schuylkill River and Lehigh River and their valleys or sub-basins.