The ceiling of the Hosios Loukas (Saint Loukas) monastery, Greece.

Listed as a UNESCO World Heritage Site, Hosios Loukas is an architectural gem, dating to the 10th century.

EXIF:
Olympus E-M1III, M.Zuiko 8-25mm f/4 Pro lens
8mm, f/9.0, 1/50 sec, ISO 6400