The Monastery of the Holy Trinity () (also known as Agia Triada, Ayías Triádhos, Ayia Triada; all meaning "Holy Trinity") is an Eastern Orthodox monastery in central Greece, situated in the Peneas Valley northeast of the town of Kalambaka. It is situated at the top of a rocky precipice over 400 metres high and forms part of 24 monasteries which were originally built at Meteora, one of the oldest still existing of the Meteora monasteries (Meteora means "suspended in the air" in Greek). Six of the 24 monasteries are still active and open to visitors. The church was constructed between the fourteenth and fifteenth centuries and is included in the UNESCO list of World Heritage Sites titled Meteora. Geography The monasteries were built on rock cliffs in the deltaic plains of Meteora. The cliffs rise to a height of more than . They are situated in the Pineios Valley within the Thessalian plains close to the town of Kalambaka. The rock cliffs, dated by chemical analysis to be 60 million years old, were created during earthquakes, and are of sandstone and conglomerate formations caused by fluvial erosion. The sediments were once in an inland sea during the Pliocene epoch. They rose as a cone during the earthquakes, forming steep rock columns, known as "heavenly columns". The area is hilly and forested, with river valleys, and a protected area known as Trikala Aesthetic Forest. The monasteries of St. Stephen and Holy Trinity are separated from the main group, which are further to the north. Prior to the twentieth century, Holy Trinity had a very difficult approach, requiring crossing a valley and climbing through the rock outcrop to reach the building's entrance. Provisions were placed in baskets drawn up by rope-ladders (now with a winch). In present day, one can walk from Kalambaka for along a foot track to reach the monastery, or use a winch-operated lift. There is a road from the back side of the cliff. It is currently reached via tunnels and 130 steps of stone. The grounds include a garden at the summit. To the northeast, there is a chapel (Ιερός Ναός Αγίου Αθανασίου) dedicated to St. Athanasius of Tzertzi (Άγιος Αθανάσιος Τζέρτζης). History The history of building monasteries on top of perilous cliffs near Meteora occurred between the 14th and 15th centuries. Even prior to this, in the 11th century, religious communities had established hermitages at the