Mount Athos is probably the most inaccessible and obscure corner of Greece. Few tourists and no women are allowed to visit the holy mountain, which is regarded as the heart of Greek Orthodox spirituality and the most sacred part of Greece.

The mountain contains almost two dozen monasteries, and although it was incorporated into the modern Greek state in 1913, it retains its autonomy as the "Athonite Theocracy" on a remote peninsula in Chalkidiki, 135 km east of Thessaloniki in northern Greece.

Despite raids by Crusaders, Catalans and Latins, and the lengthy Turkish occupation from 1424 until 1912, Mount Athos has remained virtually unspoilt since the first monasteries were established more than 1,000 years ago, and today has the world's largest and finest collection of Byzantine and post-Byzantine art.

In a gesture that is unlikely to be repeated in history, the communities on Mount Athos have agreed to allow many of their treasures and relics to go on display in a six-month exhibition at the Museum of Byzantine Culture in Thessaloniki, as part of the city's programme for the 1997 Cultural Capital of Europe.

According to the Greek Minister of Culture, Prof Evangelos Venizelos, this is probably the most important spiritual, artistic and scholarly event in the entire programme for the city this year, "the greatest exhibition project that has ever been undertaken in Greece".

Mount Athos is "the major integral living monument to Byzantine and post-Byzantine culture . . . tangible proof of the perpetuity of Hellenic civilisation," he says. But he sees the exhibition as "more than just a major cultural event. It is a noble challenge to the world to review its relationship with Time and the Word."

In all, 1,500 works of art and objects have been collected for the exhibition under the direction of Prof Athanasios Karakatsanis, with the help of monks, theologians, Byzantinologists, historians, archaeologists, architects, 80 conservators from the Ministry of Culture, and more than 300 experts in what has been described as as "an exercise in co-operation between two different worlds".

His words are echoed by Prof George Galavaris of McGill University in Canada, a member of the steering committee, who asks visitors "not to admire the exhibited relics as museum objects but as testimonies to the spirituality of the Holy Mountain".

The central focus of the exhibition is on the spirituality inherent in the every-day life of the monastic community. Monumental paintings, portable icons, rare paper icons, illuminated manuscripts, ivories and silvercraft, embroidery, wood carvings, stone carvings, sculptures, ceramics, ecclesiastical vessels, furniture and furnishings, and craftsmen's and bookbinders' tools, all illustrate the Byzantine and post-Byzantine art and history of Mount Athos and the impact it has had on the Orthodox world and modern Greek culture.

The treasures on display include 108 Byzantine and post-Byzantine icons, 120 manuscripts, 30 works of needle-craft, 131 Byzantine documents in Slavic, Romanian and Turkish, 25 seals and coins from the monasteries, 13 woodcuts, three Byzantine sculptures, six ceramics and 25 icon-casts, vestments, chalices and processional crosses.

Among the early icons is a "bema" door, made to separate the sanctuary from the main body of the church in the Vatopedi Monastery, dated circa 1200, depicting a scene from the Annunciation, showing the Virgin spinning, with the staff in her left hand and the spindle in her right.

But many of the organisers say the most beautiful icon in the exhibition, despite extensive damage to the original paint film, is a portable icon of the "Virgin Hadegetria" from Chelandri Monastery. This icon, dating from circa 1260-1270, represents an established iconographical type in which the sadness of the facial expression points to Christ's future passion. With her sad, pensive expression and spiritual beauty and the high standard of painting, this icon and the icon of Christ Pantokrator are two of the outstanding works of art painted at the end of the 13th century. According to Prof Euthymios Tsigaridas of the Aristotle University of Thessaloniki, the anonymous painter "must be regarded as one of the most outstanding artists of the Byzantine period".

The Milutin Diptych, also from Chelandri, is a 13th or early 14thcentury masterpiece. This exquisite wooden Venetian diptych, worked in wood, silver gilt, rock crystal, semi-precious stones, glass, pearls, enamel and parchment, contains 24 miniatures depicting scenes from the life of Christ painted on small parchment squares and circles, set into concavites hollowed out of the wooden surface and arranged in three rows of four in each of the two wings.

The Palaelogan painting tradition lived on in the post-Byzantine period in the Cretan school of icon painting, which came to the fore in the mid-16th century. The Cretan school is noted for its serene facial expressions, harmonious rhythms, solid closed compositions, controlled human expressions, flowing, discreet drapery and bright colours.

The Cretan school is represented in the exhibition by more than 40 icons painted by masters such as Theophanis the Cretan who worked in Stavronikita from 1549, his son Symeon and his apprentice Zorzis, Euphrosynos, and Michael Damaskinos, believed by many to have taught El Greco.

Among the treasures on display is the 14th-century Jasper chalice from Vatopedi Monastery. Dating from the second half of the 14th century, it is considered one of the most characteristic products of Byzantine work and one of the finest pieces from the Paleologan period.

The manuscripts include 42 maps collected over a three-century period, including early maps to illustrate Ptolemy's geography, and an illuminated Psalter from the end of the 9th century.

The exhibition has been given a human dimension with displays of objects from every-day life, including a large wine barrel and the complete stock of an early photographic workshop. It is enriched by special sections on the architecture of the monasteries and the natural environment of the mountain.

The lasting legacy of the exhibition, long after the treasures have returned to Mount Athos and been dispersed among the monasteries, may well be the rich, monumental catalogue edited by Dr Karakatsanis. According to Dr Tsigaridas, the 700-page volume "is the first time that a publication makes a complete presentation of the historical, religious and artistic physiognomy of the Holy Mountain".