Majorca has a few castles, as you'd expect on an island that has been invaded a number of times. Check out Capdepera Castle if you get time, plus a selection of some of the most important prehistoric sites in Majorca. The East Coast of Mallorca has a few surprises. Take time to explore!
As you leave Arta moving towards Cala Ratjada, you'll come across the 14th century Castell de Capdepera. There's a few stories and legends around this castle, along the lines of pirate sieges and a statue of the Virgin placed on the battlements, bringing about a thick fog which saw the invaders off! Well worth taking time to explore this castle in Capdepera.
Near Cales de Mallorca is what remains of a most important prehistoric village called Hospitalet Vell, probably the most important talayotic site on Majorca. Unfortunately it's looking very neglected, and doesn't get many visits. This village dates back to the second century BC, and has some pretty amazing intact treats, including a quadrangular talayot. There's a large defensive wall as well. Shame to miss it if you're staying nearby. A most important site.