Twenty-four monasteries were built on rock cliffs in the deltaic plains of Meteora. The cliffs rise to a height of more than ; and the Holy Trinity Monastery is sited
above sea level. The monasteries 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. The cliffs 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. Prior to the twentieth century, the Holy Trinity Monastery was very difficult to access, and required 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; and the monastery can be accessed via tunnels and 130 steps of stone. The grounds include a garden at the summit. To the northeast, there is a chapel () dedicated to St. Athanasius of Tzertzi (). ==History==