Castle built at the top of a hill 544 metres high, above the village of Sianna. It was an irregular enclosure with a perimeter of 175 metres, covering an area of 2,100 square metres. At the top there are the remnants of a tower or fortified house; the north side of the walls is the best preserved, with wallwalk and crenellations. The entrance must have been in the middle of the north side. There are ruins of a square tower on the NE corner and on the NW corner the foundations of a round one. Remnants of the south and east sides of the enclosure also survive. Within the walls stands a chapel dedicated to St. John. The Knights Hospitaller used Sianna as an administrative base for the control of the area spreading from Kritinia to Apolakkia; it formed a link in the communications of the south of Rhodes with the interior towards Monolithos, Apolakkia, Laerma and Istrios. The first mention of the castle in the written sources dates from 1473 and is connected to its probable abandonment.