The River Nile is over 6,700 kilimeters in length, and the longest river in the world. It is fed by various rivers, the most important of which are the Blue Nile and the White Nile. For a dry country like Egypt, the water of the river has always been vital. The annual inundation of the Nile spread fertile mud over the banks which together with the water made agriculture possible. Calling Egypt 'the gift of the Nile' is extremely apt. The ancient Egyptians thought that the waters of the Nile came from Nun, the primeval water under the earth. At Elephantine it came up through a hole in the earth. There are several Nilometers here, one of which is linked to the sacred lake of the temple of Khnum, one of the gods of Elephantine. This god's particular task was to ensure the inundation, which was itself personified as the god Hapi. In the eyes of the Egyptians, at least from the New Kingdom on, the creator god had not only taken care of Egypt by creating the Nile, but also other countries; they may not have had the Nile itself, but vegetation was nevertheless made possible thanks to rainwater, which came from a Nile in the sky.