Heliopolis was one of the oldest cities of ancient Egypt, occupied since the Predynastic Period. It greatly expanded under the Old and Middle Kingdoms but is today mostly destroyed, its temples and other buildings having been scavenged for the construction of medieval Cairo. Most information about the ancient city comes from surviving records.
The major surviving remnant of Heliopolis is the obelisk of the Temple of Ra-Atum erected by Senusret I of Dynasty XII. It still stands in its original position, now within Al-Masalla in Al-Matariyyah, Cairo. The 21 m (69 ft) high red granite obelisk weighs 120 tons (240,000 lbs).
Its native name was I͗wnw ("The Pillars"), whose exact pronunciation is uncertain because ancient Egyptian recorded only consonantal values. Its traditional Egyptological transcription is Iunu but it appears in biblical Hebrew as Ôn (אן) and Āwen (און), leading some scholars to reconstruct its pronunciation as *Āwanu. Variant transcriptions include Awnu and Annu.