The Valencian coast has been developed hard for tourism, which makes an empty stretch like this one increasingly rare and increasingly valued. The park covers about 7,744 hectares of land, and its creators were careful to exclude the urbanised zones at each end, the built-up coast near Peníscola in the north and near Alcossebre in the south. What remains inside the line is a landscape that looks much as this whole shore once did, before the cranes arrived: scrubby Mediterranean slopes running down to a coast of hidden inlets and clear water, reachable mostly on foot or by boat rather than by car.

The Serra d'Irta is a coastal range running parallel to the shoreline, its crest reaching 572 metres at the peak called Campanilles, or Campanella. Toward the south the range splits, divided by the valley of the Estopet. It is the seaward face that gives the park its drama. There the mountains do not ease gently down to a beach; they drop away abruptly, plunging in a long line of cliffs, coves and stone cornices for a dozen kilometres. Walking the coastal path, you are never far from a sudden edge, the land ending and the blue beginning with very little in between.

The reserve does not stop at the tideline. Serra d'Irta includes a marine protected area, its reefs reaching out from the base of the cliffs into the adjacent Mediterranean. Guarding the seabed matters as much as guarding the slopes above it; the rocky reefs shelter the fish, plants and invertebrates that a heavily fished and heavily visited coast can quickly strip away. By drawing the boundary to include both the mountain and the water at its foot, the park protects a single continuous system, from the ridgeline down through the cliffs and on beneath the surface of the sea.

For all its wildness, the park is framed by human landmarks. At its northern edge stands Peníscola, its old town crowded onto a rocky headland beneath the castle where the deposed antipope Benedict XIII, Papa Luna, spent his final years, an unmistakable silhouette rising straight from the sea. At the southern end lies Alcossebre, with its beaches and marina. Between the two, Serra d'Irta keeps a quieter kind of value, not the postcard fortress or the packed resort, but simply the coast itself, left alone. In a region that has sold so much of its shoreline, that restraint is its own monument.

To experience Serra d'Irta is to slow down. With no coastal road cutting through the protected stretch, the coves and cliffs are reached mostly on foot or by boat, along tracks that follow the ridge or hug the shoreline. That inaccessibility is exactly what has preserved the park's character; the hidden inlets stay hidden because reaching them takes effort. Walkers trade the convenience of the resort beaches for something rarer, a shoreline where the loudest sound is the sea working at the rocks and the crowds thin almost to nothing. Inland, the trails climb through low Mediterranean scrub, rosemary and thyme and the tough fan palms of these hills, toward the crest at Campanilles. From the high ground the whole shape of the place resolves: the mountain running parallel to the coast, the abrupt seaward drop, the ribbon of protected water at its foot. It is a landscape best understood by moving through it slowly, which is perhaps the surest measure of how much this stretch has kept that the rest of the coast has lost.