The grand ancient temple of Baalbek, located in the ancient Phoenician city of Baalbek in Lebanon’s Beqaa Valley, about 85 kilometers northeast of Beirut, was dedicated to the Phoenician sky-god Baal and his spouse, Astarte, the Queen of Heaven. Inhabited as early as 9000 BC, Baalbek grew into an important pilgrimage site in the ancient world for offering worship in that temple, situated in the centre of the city. Much later, the Roman temple of Jupiter Baal was erected on its ruins.

Baalbek was conquered by Alexander the Great in 334 BC, who renamed it Heliopolis, the City of the Sun. The name was still in use in 64 BC, when Pompey the Great, a military and political leader of the late Roman Republic, annexed the Phoenicia region for Rome and in 15 BC it became a colony of the Roman Empire. The Romans decorated the city with massive building projects, along with roads, walkways and aqueducts and during the reign of the Emperor Septimus Severus (193-211 CE) the grand temple of Jupiter Baal was built, which was the largest and the most ornate religious building in the entire history of the Roman Empire. However, the temple of Bacchus, which still stands, is larger than the Parthenon of Athens and all the other temples of the Roman complex, which includes the temples of Jupiter, Venus, Mercury and Bacchus. With the adoption of Christianity by Constantine in the Roman Empire, many pagan sites were destroyed, however these temples were spared through their use as churches and they continued in their role as Christian places of worship until the invasion of the Muslims in 636 AD.

After the Muslim invaders defeated the Byzantine forces at the Battle of Yarmouk in the month of August 636, they used it as a reinforced fortress, named it Al-Qalaa, the fortress and also added a mosque amid the ancient Roman temples, while the constructions by the Christian were torn down and destroyed drastically. Later, the Byzantine army sacked the city twice, in 748 and in 975, but they failed to hold it.

Finally, after having survived the Mongols and other military campaigns, it passed into the Ottoman Empire which largely ignored the city and allowed the ruins to crumble. Apart from that, earthquakes, storms and and other natural forces continued to damage the site till 1898, when the German Emperor Wilhelm II visited the area and sent a team of archaeologists to begin work there for restoring and preserving the site for the future generations.

The discovery of the cornerstones of the earlier temple made the scientists and the historians mystified, since they weigh over 100 tons and the retaining wall monoliths weigh 300 tons each. It is an enigma, as to how those huge stones were moved. In fact, the architecture and the magnitude of the temples of Jupiter, Bacchus and Venus have created ripples of a puzzle for the archaeologists, as they continuously theorize as to how rocks of this grandeur could have been carved and assembled. The temple of Jupiter is surrounded by 54 columns, which are nearly 23 m high and are considered some of the largest in the world.

The temple of Bacchus at Baalbek was commissioned by the Roman Emperor Antoninus Pius and was constructed between 150 AD and 250 AD. It stands out from the rest and was built close to the courtyard in front of the larger temple of Jupiter-Baal. This temple is rather well preserved, because when the temple complex became damaged and dilapidated, the Temple of Bacchus was protected by the rubble of the rest of the site's ruins

Compared to the temple of Jupiter, the temple of Bacchus is slightly smaller and is 66m long, 35m wide and 31m high. It consisted of 42 Corinthian columns, nineteen of which still remain upright in position standing 19 m high. The inner chamber is decorated with two levels of niches on each side, which contain scenes from the birth and life of Bacchus. The inner chamber (adyton) stands above a flight of steps.

The ruins of Baalbek, including the temple of Bacchus, are enlisted in the World Heritage Site in 1984.