Cabo Prior is the high, cliff-edged headland north of Ferrol where the Atlantic meets the open ría. The lighthouse on its summit, built in 1854, still works — a slim white tower beside a granite keeper's house, perched well over a hundred metres above the surf with one of the bigger Galician views: south to the entrance of the Ría de Ferrol, north along the Costa Ártabra toward Cabo Ortegal, and west across nothing but ocean.
The real curiosity, though, is what surrounds the lighthouse on the slope below. From the late 1930s onward, the Spanish army built a substantial coast-artillery position here — six Vickers 152mm naval guns in armoured emplacements, plus magazines, fire-control bunkers, and barracks — to defend the approach to the Ferrol arsenal. The guns were stripped in the 1990s but the concrete works remain. You can wander the access road and turn-offs to peer into the casemates and bunker entrances; some are open, some sealed. It is freely accessible and quite atmospheric in fog. The cliffs themselves are excellent for sea-bird watching, and the path continues down to Praia de Ponzos, one of the wildest beaches near Ferrol.