Kastro (meaning "castle, fortress") is set on the highest point of Plaka
. It is a village within the village - the place where the first houses of the village were built for better protection. Today only ruins of the castle can be seen but some of the houses are still in their original outlook. On the top of Kastro stands the church of Messa Panagia from which you can observe spectacular sunsets over the sea and the islet of Andimilos.