First, head to Hondarrabia, a small fishing village on the Spanish border. For a more traditional excursion and a great family outing, take the boat in Hendaye which drops you off right at the port.
The walk through the small village's bustling streets to the old town will take you along the fortress wall, where you can enjoy stunning views of the entire bay. For either lunch or dinner, head to Rue San Pedro: a little jostling is required, but you will be well-rewarded with stewed chipirones, Bellota ham, and a glass of Rioja. This is also the place to go for the best pintxos in the entire Basque region: every bar and restaurant has its own speciality, often with its roots in a secret family recipe.
You will find the same party atmosphere in San Sebastián's casco viejo ("old town"). The best strategy is to visit in the afternoon: a stroll along the full length of the pier and a trip to the Museo de San Telmo are a must, as is a visit via cable car to the Monte Igueldo theme park and its unmissable panoramic viewpoint. If that makes you feel dizzy, the city aquarium will immerse you in the beauties of the underwater world instead. To end the day in style, hit the tapas bars.