Keldur is turf house whose oldest part dates back to the 13th century. The site is mentioned in some of the main Icelandic sagas, such as Njáls saga and Sturlunga saga. One of the most prominent medieval chieftains, Jón Loftsson, lived here and let build a monastery. The site includes several rooms to be visited with objects from different ages, and a church which includes ancient objects, including two wooden statues dating to the Catholic period (before 1550). I recommend getting a guided tour to fully understand the significance of this site.