The largest city of the Basque Country, Bilbao is magnificent mix of historic and spectacular modern architecture. Head to Casco Viejo to meander medieval streets and sample some of the best pinxtos (tapas) around. And don’t miss the massive, ultramodern Guggenheim Museum Bilbao across the river, featuring the works of leading artists of the 20th century. Clad in glimmering titanium, this enormous structure is a work of art itself.