The byzantine Monastery of Daphni lies to the west of Athens, at the foot of Mount Aigaleo in Haidari, almost half-way along the ancient Sacred Way from Athens to Eleusis. According to Pausanias, in the same area there was an enclosed temple dedicated to Apollo ?Daphnaios? or ?Daphnios?, Demeter and her daughter Persephone.

The monastery is protected by a massive square fortification with high walls, inside which looms the Katholicon (the main church), with a perimeter colonnade and cells for the monks adjacent to the south side of the church, forming a small churchyard.

The Katholicon of the monastery dates back to the 11th century. It belongs to the characteristic type of the Hellenic octagonal cross-in-square church, adopted by some very important monuments of the middle-byzantine period, such as the Catholicon of the Monastery of Ηοsios Loukas in Boeotia and that of the Nea Moni in Chios. The main characteristics of this architectural type are the big dimensions of the dome and the way it is supported ? through four squinches ? by eight pillars, symmetrically placed at the sides of the square central space of the nave defining an octagon. Four side chapels occupy the corners of the building.

The narthex on the west side of the church was built concurrently with the Katholicon, whereas a short while later an exonarthex (portico) was added, in the form of an open colonnade with a storey. As a result of a major earthquake that caused severe damages during the period of the Frankish occupation, the monks of the Cistercian order, to which the monastery was granted in 1207 by the Duke of Athens, Otto de la Roche, implemented extended restoration works in the exonarthex, giving it its present form, with the pointed arches on the facade and the crenellations on the upper floor.

The simple cloisonne masonry of the Katholikon is enriched by brick ornamentation around the windows, while the interior is decorated with high quality mosaics, on a gold background, marble revetments and sculpted decoration, from which very few examples are preserved nowadays. The architectural type and the luxurious marble and mosaic decoration connect the foundation of the monument with circles of the imperial court of Constantinople. The mosaics that decorate the upper parts of the wall surfaces illustrate the doctrine of the church, following the established iconographic program of the middle-byzantine period. The slender figures, with their gentle faces, the excellent proportions and the moderate movements, refer to ancient Classical and Hellenistic exemplars.

The frescoes on the lower parts of the nave, partly preserved nowadays, were painted in 17th century, in the place of the destroyed marble revetments.

To the north of the Katholicon there are the ruins of the byzantine Refectory (the dining hall of the monks).

The enclosure has the form of a square defensive wall, with three towers reinforcing the northern side, a continuous pathway supported on wide ?blind? arches, crenellated battlements and two entrance gates on the eastern and western part. Parallel to the walls, with the exception of the southern side, there are the surviving foundations of buildings which probably housed the original Byzantine cells of the monastic complex.

After the conquest of Athens by the Ottoman Turks in 1458, the monastery was given back to the orthodox monks, who constructed two storey buildings containing cells, storage rooms, a refectory and a gallery in the small churchyard to the south of the Katholicon. The architectural remains that were discovered during excavations to the south and west of the churchyard probably belong to buildings of auxiliary use from the byzantine period.

During the Greek Revolution of 1821 the monastic complex was occasionally used as a garrison. After the founding of the New Hellenic State (1830), the monastery was deserted and finally abandoned, after having housed, for a short while, barracks for the Bavarian (1838-1839) and French (1854) troops and the Public Psychiatric Hospital (1883-1885).

The restoration works of the monastic complex and of the mosaics of the Catholicon began at the end of the 19th c. and have been continued, periodically, up today by the Ministry of Culture and intensified after the disastrous earthquake in 1999, financed by European Funding Programs and the Greek State.

Since 1990, the Monastery of Dafni is inscribed in the World Heritage List (WHL) of UNESCO, as a serial registration along with the Monastery of Ηοsios Loukas in Steiri of Boeotia and Nea Moni in Chios, as they share the same architectural type and aesthetic characteristics of exceptional art.