Platja de les Arenes is the beach Valencia keeps closest to hand: broad sand, Mediterranean water, and a promenade lined with restaurants at the edge of the old maritime quarter. It is not the wildest or quietest beach in the region, but it is the one that best explains how Valencia uses the sea as part of daily life rather than as a distant excursion.
Come for a swim, a long walk north toward Malvarrosa, or lunch within sight of the water. The classic move is paella by the beach, though prices and quality vary, so do not sit at the first terrace that waves a menu at you. The beach gets busy in summer, but its size absorbs crowds better than you might expect.