Baalbek (ˈbɑːlbɛk,_ˈbeɪəlbɛk; Baʿlabakk; Syriac-Aramaic: ܒܥܠܒܟ) is a city located east of the Litani River in Lebanon's Beqaa Valley, about northeast of Beirut. It is the capital of Baalbek-Hermel Governorate. In Greek and Roman times, Baalbek was also known as Heliopolis (Ἡλιούπολις, Greek for "Sun City"). In 1998, Baalbek had a population of 82,608, mostly Shia Muslims, followed by Sunni Muslims and Christians.
It is home to the Baalbek temple complex which includes two of the largest and grandest Roman temple ruins: the Temple of Bacchus and the Temple of Jupiter. It was inscribed in 1984 as an UNESCO World Heritage site.
A few miles from the swamp from which the Litani (the classical Leontes) and the Asi (the upper Orontes) flow, Baalbek may be the same as the manbaa al-nahrayn ("Source of the Two Rivers"), the abode of El in the Ugaritic Baal Cycle discovered in the 1920s and a separate serpent incantation.
Baalbek was called "Heliopolis" during the Roman Empire, a latinisation of the Greek Hēlioúpolis (Ἡλιούπολις) used during the Hellenistic period, meaning "Sun City" in reference to the solar cult there. The name is attested under the Seleucids and Ptolemies. However, Ammianus Marcellinus notes that earlier "Assyrian" names of Levantine towns continued to be used alongside the official Greek ones imposed by the Diadochi, who were successors of Alexander the Great. In Greek religion, Helios was both the sun in the sky and its personification as a god. The local Semitic god Baʿal Haddu was more often equated with Zeus or Jupiter or simply called the "Great God of Heliopolis", but the name may refer to the Egyptians' association of Baʿal with their great god Ra. It was sometimes described as Heliopolis in Syria or Coelesyria (Heliopolis Syriaca or Syriae) to distinguish it from its namesake in Egypt. In Catholicism, its titular see is distinguished as Heliopolis in Phoenicia, from its former Roman province Phoenice. The importance of the solar cult is also attested in the name Biḳāʿ al-ʿAzīz borne by the plateau surrounding Baalbek, as it references an earlier solar deity and not later men, named Aziz.