The Holy Belt, according to tradition, was made by the Blessed Virgin Mary herself with camel hair. Originally it was kept in Jerusalem and later in Constantinople. During the reign of Emperor Arcadius (395-408), the precious Belt of the Mother of God was brought from Zela of Cappadocia to Constantinople, and placed in the Church of the Theotokos in the section of Chalcopratia. In 458 it was transferred by the Emperor Leo VI the Wise to the Blachernae church. The Empress Zoe, wife of Leo VI the Wise, out of gratitude for a miraculous cure, embroidered the Belt with gold thread, as it is found today, but divided it in three pieces. During the 12th century under Manuel I Komnenos (1143-1180) an official holiday for the Belt was established on August 31st; previously it had shared the Feast of the Vesture of the Virgin on 1 July.
In the 12th century, when, in the course of a defeat of Isaacius by the Bulgar King Asan (1185), the Holy Belt was stolen and taken to Bulgaria, and from there it later came into the hands of the Serbs. It was presented to Vatopaidi by the Serbian Prince Lazarus I (1372-1389), together with a large piece of the True Cross. Since then it has been kept in the sanctuary of the katholikon.
Under Turkish rule, the brethren of the Monastery took it on journeys to Crete, Macedonia, Thrace, Constantinople and Asia Minor, to distribute its blessing, to strengthen the morale of the enslaved Greeks and to bring freedom from infectious diseases.
Numerous are the miracles that have taken place up to today with the Holy Belt. Its value is priceless because it's associated to the Blessed Virgin Mary. She has the grace and to her the miraculous power is attributed, which in many ways she transmits to the faithful.
The Holy Belt maintains unaltered the grace of the Most Holy Theotokos, because it became connected with her person and her life and because saints are Spirit-carriers during not only their life, but also after their death. The same phenomenon is mentioned in the Holy Scriptures when objects that the Prophet Elijah and the Holy Apostles wore actually performed miracles, because they had the grace of the saints. For this reason the Church attributes it honorary worship, as it does to the Holy Wood of the Cross of the Lord.
For more information on the Holy Belt on the island of Santorini, see here, here and here.
More contemporary miracles, especially to holy Elders of our times, can be read here.
For information on pieces of the Holy Belt in the Roman Catholic Church, see here.