On its high perch at the top of Chora, the Monastery of St. John the Theologian is one of the world's best-preserved fortified medieval monastic complexes, a center of learning since the 11th century, and today recognized as a UNESCO World Heritage Site. Hosios Christodoulos, a man of education, energy, devotion, and vision, established the monastery in 1088, and the complex soon became an intellectual center, with a rich library and a tradition of teaching. Monks of education and social standing ornamented the monastery with the best sculpture, carvings, and paintings and, by the end of the 12th century, the community owned land on Leros, Limnos, Crete, and Asia Minor, as well as ships, which carried on trade exempt from taxes.
A broad staircase leads to the entrance, which is fortified by towers and buttresses.
The complex consists of buildings from a number of periods: in front of the entrance is the 17th-century Chapel of the Holy Apostles; the main Church
dates from the 11th century, the time of Christodoulos (whose skull, along with that of Apostle Thomas, is encased in a silver sarcophagus here); the Chapel of the Virgin is 12th century.
The Treasury contains relics, icons, silver, and vestments, most dating from 1600 to 1800. An 11th-century icon of St. Nicholas is executed in fine mosaic work and encased in a silver frame. Another icon is allegedly the work of El Greco. On display, too, are some of the library's oldest codices, dating to the late 5th and the 8th centuries, such as pages from the Gospel of St. Mark and the Book of Job. For the most part, however, the Library is not open to the public and special permission is required to research its extensive treasures: illuminated manuscripts, approximately 1,000 codices, and more than 3,000 printed volumes. The collection was first cataloged in 1200; of the 267 works of that time, the library still has 111. The archives preserve a near-continuous record, down to the present, of the history of the monastery as well as the political and economic history of the region.