Halki Castle is located on the hill of St. Nicholas over the old village of Halki. It was built by the Knights of St. John in the 14th-15th century over the ancient Hellenistic citadel. From there they were able to control the sea routes, the harbor and the Trachean peninsula. Inside the castle are the ruins of the medieval church of St. Nicholas. At the gate the emblem of the Grand Master of the knights Pierre d’Aubusson (1476-1503) is engraved.
Today, the castle is accessed through a paved path from where the view is just fascinating. The back side of the hill is rough and its slopes lead to the sea. At the foot of the castle, there are three small chapels dedicated to Virgin Mary, to Saint Nicolas, and to the Holy Trinity.
References:The Basilica of Santa Maria in Trastevere is one of the oldest churches of Rome. The basic floor plan and wall structure of the church date back to the 340s, and much of the structure to 1140-43. The first sanctuary was built in 221 and 227 by Pope Callixtus I and later completed by Pope Julius I.
The inscription on the episcopal throne states that this is the first church in Rome dedicated to Mary, mother of Jesus, although some claim that privilege belongs to the Basilica di Santa Maria Maggiore. A Christian house-church was founded here about 220 by Pope Saint Callixtus I (217-222) on the site of the Taberna meritoria, a refuge for retired soldiers. The area was made available for Christian use by Emperor Alexander Severus when he settled a dispute between the Christians and tavern-keepers.
The church underwent two restorations in the fifth and eighth centuries and in 1140-43 it was re-erected on its old foundations under Pope Innocent II.