Rannu first appears in 1471, when a stone vassal castle of the Tiesenhausens stood here, which is why the Germans called it Schloss Randen. Over the centuries it passed to the Campenhausens, the Sivers and the Bergs, and the house grew in stages. In 1973 it was torn down for a collective-farm center, and of the medieval castle only mounds and ditches remain.