There’s a 34m tall lighthouse on a rocky headland just a few towns east of my rented apartment on Spain’s Costa de la Luz. At night I liked to sit on the balcony with a glass of wine and watch its spectral eye flash a warning through the inky darkness. The cape has a long sandy beach that’s a favourite of hippies and windsurfers based in the nearby town of Los Caños de Meca. But this unassuming...