Rakkei (落慶) refers to celebration of new construction or the completion of repairs to temples and shrines.
落' means '落成' (completion), which was a festivity when the Imperial Court was completed in China. This was extended to use when temples and shrines are constructed and newly built for a diversion. And the ceremony to be held on that occasion is called Rakkei hoyo, Rakusei keisane or Rakusei shiki, and so on.
In Rakkei hoyo, the Buddha statue as the honzon (principal image of Buddha) (or Mandala (a diagram that depicts Buddhist deities according to certain geometric formats and illustrates the Buddhist world view) and so on) is enshrined, and Kaigen hoyo (Eye-opening ceremony) is held as a ceremony to put the spirit into the honzon in order to celebrate the completion of the work, or to pray to and congratulate the Buddha, the founder of the religious sect or the ancestors related to the temple as it stands.
It is said that the sky often has a good sign such as 'saiun' (glowing clouds), 'nichiun' (ring around the sun) or 'rainbow' on such an auspicious event.