This description of Meteora is taken from the Wikipede website, my thanks to them for an excellent explanation.
The Meteora (/ˌmɛtiˈɔːrə/; Greek: Μετέωρα, pronounced [meˈteora]) is a rock formation in central Greece hosting one of the largest and most precipitously built complexes of Eastern Orthodox monasteries, second in importance only to Mount Athos. The six (of an original twenty four) monasteries are built on immense natural pillars and hill-like rounded boulders that dominate the local area. It is located near the town of Kalabaka at the northwestern edge of the Plain of Thessaly near the Pineios river and Pindus Mountains.
As early as the eleventh century, monks occupied the caverns of Meteora. However, monasteries were not built until the fourteenth century, when the monks sought somewhere to hide in the face of an increasing number of Turkish attacks on Greece. At this time, access to the top was via removable ladders or windlass. Currently, getting up there is a lot simpler due to steps being carved into the rock during the 1920s. Of the 24 monasteries, only six (four of men, two of women) are still functioning, with each housing fewer than ten individuals.
Meteora is included on the UNESCO World Heritage.
The name means "lofty", "elevated", and is etymologically related to meteor.