Begin your trip to San Sebastian exploring its Old Town. Take a stroll through the cobbled streets and admire the historic architecture of the buildings in this maze and be transported back to ancient times. Visit the Gothic Church of Saint Vincente and the Baroque-style Basilica of Saint Mary of the Chorus. Also, don't forget to indulge in pintxos (Basque tapas) at one of the bars on Calle 31 de Agosto.
Start the day relaxing on the sandy Zurriola Beach, perfect for surfing. Afterward, head to Mount Igueldo, and enjoy the Igueldo funicular ride with scenic views, and hike to the top. Here, experience the panoramic views of San Sebastian, the La Concha bay, and the Cantabrian coast. Visit the ancient iron lighthouse Tower of Igueldo, dating back to 1855. Once you get back down, go swimming at the city's main attraction, La Playa de la Concha.
On the final day, take a day trip first to Hondarribia, a small town in Spain near the French border. This town has a fantastic old quarter which has buildings dating back to the 14th century. From here, take a short ferry ride across the border to Hendaye beach in the French Basque Country. This beach is famous for its clear water and family-friendly facilities. End the trip with a seafood dinner back in San Sebastian.
If you have an extra day to spend, consider doing a Basque Wine Tour at Getaria or drive to the nearby French cities of Biarritz and Bayonne. Those with less time can condense day three's activities to visit only Hondarribia.