During the fourth crusade, crusaders were amazed by the Muslim and Byzantine fortresses they conquered. After settling on conquered lands they would often build new castlesthat would serve as border inspection posts, administration centers, secure shelters and military bases. In order to build them, they chose spots that offered protection from raiders or opposing armies and in many cases they would incorporate elements from local architecture.
When the dynasty of Sanudo came to Paros, the Venetian Duke of Naxos Marco Sanudo decided to build the castle of Parikia, using marble from ancient Greek temples. Inside the Frankish castle of Parikia there is the Christian Orthodox Church of Agios Constantinos. This castle is one of the most important post byzantine monuments of the Cyclades islands. In later history the Venetians built the castle of Naoussa and the castle of Kefalos which is situated on Agios Antonios hill next to the village of Marpissa.
Source: ParosEasyBooking.gr – The Frankish Castle