Heliopolis, the center of sun worship in ancient Egypt, called On in the Bible. Heliopolis, a Greek word, means “city of the sun.” (The Greeks applied this name also to Baalbek in Syria.) Heliopolis was near the site of modern Cairo.

The city was a center of learning, notable particularly for its schools of astronomy and philosophy. It declined after Alexandria was founded in 332 B.C., and the site eventually was deserted. One obelisk from about 2000 B.C. still stands. Other obelisks, known as Cleopatra's Needles, have been removed—one to London, another to New York City.