Harir Castle is known locally as Xanzad Castle, but Harir Castle or قهڵای خرواتانقلعة خرواتان Khrouattan Castle (after the adjacent municipality or village, respectively) are better names since there is another place nearby also Xanzad Castle.
Access to the castle is not particularly well-marked. One must ask for directions, then park at a water pump station and make the way up the mountain on good faith. A pair of eagle-eyes will spot a ruined wall visible from the foothills, but the ruins are otherwise challenging to see because they are built amid same-colored rocks that disguise and obscure them. They are atop a peak next to Mount Bani Harir.
Dating to the 16th CENT CE, Harir Castle is a 1000 square meter campus of mountaintop ruins surrounded by a four- to six-meter masonry fortification wall. There are five domed watchtowers: three in the north, and two to the west (built into the fortification wall). There are also 25 carved pits for storing rainwater. Archaeological excavations found stone arrows and coal dating to the Middle Stone Age, 15th MILL BCE - 10th MILL BCE.
A detour at the base of the mountain (and these are easy to make until you are certain you found the trail) takes you to an amazing cave that is itself a worthwhile destination.