The nilometer is an ancient device used to measure the level of the waters of the Nile River.
These measurements were crucial in Ancient Egypt, as the level of the Nile determined the fertility of agricultural land and therefore the annual harvest.
A nilometer could consist of a graduated column, a stone staircase or a well connected to the river. Priests and officials analyzed these measurements to predict floods and plan the distribution of resources.
The best-known nilometers are found on the island of Rhodes, in the temple of Kom Ombo and in Elephantine