Castelo de Paderne is one of the best reasons to leave Albufeira's beach strip for the inland Algarve. The ruined castle sits above the Quarteira River and preserves the outline of a medieval Islamic fortification built largely in rammed earth.
It is a spare, atmospheric site rather than a restored castle with exhibits. Go for the walk, the red walls, the countryside, and the sense that the Algarve's history reaches well beyond resort towns and fishing beaches.