Las Siete Calles or Casco Viejo in Spanish or Zazpikaleak or Alde Zaharra in Basque are different names for the medieval neighbourhood of Bilbao, part of the Ibaiondo district.

Later the town expanded northwards with the construction of the Plaza Berria or Plaza Nueva (new square) and the streets Santa María ("Saint Mary"), Bidebarrieta ("new ways"), Correo ("mail") and Askao.

The area is probably the most colorful part of Bilbao, including many shops and taverns, several historical churches (San Antón, Santos Juanes, the Cathedral, San Nicolás), a large food retail market ( Mercado de la Ribera ), the public Arriaga Theatre, the seat of the Academy of the Basque Language (Euskaltzaindia), a ball court, and a public library.

Three public elevators also connect Casco Viejo to the neighbourhoods of Begoña and Solokoetxe, which otherwise demand a rather intense uphill walk.

There is a tradition of middle-age men doing a tavern crawl drinking short glasses (chiquitos) of wine and singing choral songs.