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 Church of St Donatus name refers to Donatus of Zadar, who began construction on this church in the 9th century and ended it on the northeastern part of the Roman forum. It is the largest Pre-Romanesque building in Croatia.
The beginning of the building of the church was placed to the second half of the 8th century, and it is supposed to have been completed in the 9th century. The Zadar bishop and diplomat Donat (8th and 9th centuries) is credited with the building of the church. He led the representations of the Dalmatian cities to Constantinople and Charles the Great, which is why this church bears slight resemblance to Charlemagne's court chapels, especially the one in Aachen, and also to the Basilica of San Vitale in Ravenna. It belongs to the Pre-Romanesque architectural period.
The circular church, formerly domed, is 27 m high and is characterised by simplicity and technical primitivism.