Built to defend the town against marauding tribes from the interior, 200-year-old Bilad Sur Castle boasts unusually shaped towers. It has been closed for an extended period for restoration, but you can wander around the outside. To reach the castle, turn left off Hwy 23 (Main St) at an elaborately kitsch residence, 1.3km from the clocktower roundabout at the Muscat end of town.