Portugal's Fisherman's Trail is 226 kilometers long, follows ancient paths carved by fishermen to reach their nets on the Atlantic cliffs, and was named one of the six most beautiful coastal trails in the world by Condé Nast Traveler.
It is also walkable by anyone in their sixties or seventies who is basically fit.
I published a practical guide on season, shoes, poles, sand gaiters, accommodation, luggage transfer, navigation, and preventing blisters in The Curious Wanderer.