Kastro is a historic village located on the island of Sifnos in the Cyclades archipelago of Greece. Known for its well-preserved architecture, Kastro features narrow streets, whitewashed houses, and stunning views of the Aegean Sea. The village was built in the 15th century as a fortress to protect its inhabitants from pirate attacks. The village is home to several important churches, including the Church of the Seven Martyrs, which is a popular spot for visitors. Kastro's unique charm and rich history make it a significant cultural site on Sifnos, attracting tourists interested in exploring traditional Greek island life.