Forming the heart of Bilbao's Casco Viejo are seven streets known as the Siete Calles (Zazpi Kaleak in Basque). These dark, atmospheric lanes – Barrenkale Barrena, Barrenkale, CarnicerÃa Vieja, Belostikale, TenderÃa, Artekale and Somera – date to the 1400s, when the east bank of the RÃa del Nervión (RÃa de Bilbao) was first developed. They originally constituted the city's commercial centre and river port; these days they teem with lively cafes, pintxo bars and boutiques.