Concierge.com's insider take:
The most central of Bilbao's shopping areas is the Gran Vía Don Diego López de Haro, known locally as Gran Vía. This wide avenue, and the streets that radiate out from its intersection with the circular Plaza Moyúa, have lots of upscale clothing and accessory boutiques, including Carolina Herrera, Donna Karan, and Ermenegildo Zegna. There are also design shops, bookstores, and music outlets. Start at the intersection of Gran Vía and Calle Gregorio de la Revilla and work your way northeast, toward the Casco Viejo.