Here's why:
* The Basque Country is divided: It's split between Spain and France.
* Spanish Basque Country (País Vasco): The capital of the autonomous community of the Basque Country in Spain is Vitoria-Gasteiz.
* French Basque Country (Pays Basque): There's no single capital in the French Basque Country. It's considered a region with several important cities, such as Bayonne, Biarritz, and Saint-Jean-de-Luz.
So, depending on which part of the Basque Country you're referring to, the "capital" varies.