  thumb|250px|delika canyon and waterfall from burgos side. the nerviÃ³n river runs through the city of bilbao, spain into the cantabrian sea (bay of biscay). its lowermost course, downstream of its confluence with the ibaizabal river, is known as the estuary of bilbao. ==geography== the river is  long from its source at the burgos and alava provincial limits to the sea and runs in south to north direction. soon after its source, the river forms a spectacular  waterfall in the delika canyon (alava) and then enters the biscay province through the town of orduÃ±a. it goes into alava again through the towns of amurrio and llodio. then the river runs again into the biscay province until the cantabrian sea, entering the bilbao metropolitan area at ugao-miraballes. the tidal influence reaches  inland from the sea, at bilbao's old town. the main tributaries are: * from the west:cadagua and galindo. * from the east: arratia, ibaizabal and asua. ibaizabal is considered by some to be an equally important river, so the whole system is often called nervion-ibaizabal and the final tract just 
Geography_of_Bilbao Geography_of_Biscay Rivers_of_Spain Rivers_of_Alava