Perched at an improbable, almost comical angle on a gigantic fist of rock, Castell d'Alaró is one of the most rewarding castle climbs on the island. The ruins are all that remain of the last redoubt of Christian warriors who could only be starved out by Muslim conquerors around 911, eight years after the Moors invaded Mallorca. The astonishing views, from Palma to Badia de Alcúdia, are something special. If the two-hour walk up doesn't appeal, you can cover most of the ascent by car.
The first 4.2km to nearby Es Verger restaurant are paved but have their fair share of potholes. The road deteriorates (but should be OK if it hasn't rained – ask at the restaurant for the current state of the road) for a further 1.2km beyond the restaurant to a parking area at the base of a path that leads (in 15 minutes) to the ruins. Once there, you'll see several arched stone doors and wall remnants of what was once clearly a major fortress.
Another minute's walk uphill brings you to the Ermita de la Mare de Déu del Refugi, a decrepit 17th-century chapel that locals still visit to give thanks for miraculous events.
If you can't bear to leave, bed down at the Hostatgeria Castell d'Alaró.