Trilithon of Baalbek, Ancient megalith in Baalbek, Lebanon.

The Trilithon of Baalbek is a row of three limestone blocks in the western supporting wall of the Temple of Jupiter, set about 7 meters up. Each block measures roughly 21.3 meters long, 4.8 meters high and 4 meters wide, weighing an estimated 800 tons. In the photo, the lowest course of the wall consists of enormous rectangular blocks with rough, weathered faces, with smaller blocks above and loose stone fragments at the base.

The three limestone blocks were set into the western supporting wall of the Temple of Jupiter at a height of about 7 metres. No written testimony from the builders survives, and no extraction or transport method is accepted by the scientific community. The quarry is thought to lie about 900 metres away, slightly above the terrace, so the stones could be moved downhill on rollers; levers and capstans are the proposed mechanisms.

The name Trilithon comes from the Greek for "three stones". The blocks were set without mortar, and their joints are so tight that a knife blade barely fits between them. Local tradition long attributed the wall to giants or jinn, and in 1968 Erich von Däniken cited it as evidence of alien contact in Chariots of the Gods?.

The site is open daily for visitors who want to examine these foundation stones up close, and sturdy footwear is essential for navigating the rocky terrain. Set aside enough time to walk around the full temple complex and view the stones from different angles.

The three blocks sit about 7 metres up in the wall, and no ancient writer describes them: no contemporary written testimony survives from Baalbek. The quarry that probably supplied them lies some 900 metres away, slightly above the terrace, so the stones could be rolled downhill. Erich von Däniken used the Trilithon as evidence of alien contact in his 1968 book Chariots of the Gods.