Built tight against the defensive walls, this archaeological museum has a mix of interesting finds from the town and around. The modern building was constructed around an 18m-deep Moorish well with a spiral staircase heading into the depths that you can follow for a short stretch. Otherwise, this is another Algarve museum that starts at the prehistoric beginning but soon moves on to focus on the Almohad period of the 12th and 13th centuries.
Other interesting artefacts include a solid-gold Roman coin from the 370s AD and some still-serviceable 17th-century pottery. When you've seen everything, head out onto the viewing platform to gaze down into some typical Algarve backyards.