Walk through Palma’s old town and you might miss it. A narrow gap between weathered stone facades leads toward Carrer de l’Almudaina. But slow down. Look through the wide portal of Ca n’Oleo, and something stops you in your tracks. Beyond the shadowy entrance, the courtyard opens into a flood of light. Right in the center sits a sculpture glowing in an electric shade of grass green: Posidònia by Juan Carlos Nadal. Visitors who weren’t even looking for art find themselves drawn in anyway. They…