In Mount Iguelo's Amusement Park, you'll find one of the best viewpoints in San Sebastian (I think it's a must-see). From there, you can, at a glance, the whole coast of San Sebastian, even beyond the city, the entire Basque coastline and its interior.
San Sebastian is a history with a long, varied and unique history - a military encampment in the fifteenth century, a tourist area for French and Spanish bourgeousie, and a royal resort in the nineteenth century. Today it's a lovely city with unique natural areas like the Bay of La Concha, the elegant buildings that line the promenade, the Alderdi Eder Gardens, the harbour, Mount Urgull ... the three city beaches are great, with La Concha being the best. I'm not much of a writer, but take a look at these photos and videos and you can see a small sample of what awaits you in this amazing city.