Alahan Monastery (Turkish: Koja Kalessi)[1] is a complex of fifth-century buildings located in the mountains of Isauria in southern Asia Minor (Mersin province in modern day Turkey).

The complex played a significant role in the development of early Byzantine architecture, and practically everything known about it can be attributed to the excavations of Michael Gough.

[3] The complex contains two churches, rock-cut chambers, a baptistery, living quarters, and many other spaces, like a forecourt, necropolis, bathhouse, and lower terrace.

There is debate about the monastery's original purpose, but it nonetheless became a communal living space for monks and those seeking pilgrimage until the seventh century AD, at which point it became abandoned.

[3] Alahan is a key site in the history of early Byzantine architecture, half a century before the great achievements of Anicia Juliana and Justinian in Constantinople.

[5] Gough's excavation discovered decorations of sculpted masonry and rich mosaics, which suggests that the church had wealthy patronage during its time.

[5] A twin-apsed baptistery with two aisles, oriented east-west, with an entrance to the south through the north wall of the colonnaded walkway.

It is believed that it was built as the community at Alahan expanded, as a font located in the cave church likely served as the original baptistery.

"[7] The first European visitor Count Leon de Laborde who arrived in 1826 was enthusiastic but inaccurate in his written accounts of the monastery.

[7] This was followed by the English cleric, A.C. Headlam, who wrote an exhaustive article which gives meticulous detail to the monastic complex as well as the church located at the east end.