The sanctuary of Jupiter Heliopolitanus in Baalbek sits highup in the Bekaa Valley among the mountains of Lebanon. It was one of the most impressive building complexes of the Roman Imperial period. Although the region was inhabited from the seventh millennium BC onward, large stone cult buildings seem to develop only in the late Hellenistic period. The large temple in the enormous, 270-metre-long sanctuary of Jupiter was completed under the reign of Emperor Nero (r. AD 54–68). It was surrounded by a pseudodipteral colonnade of 10 x 19 Corinthian columns. A wide set of steps led from the sanctuary courtyard to the floor of the temple some 6 m above ground level, while the ridgeline of its roof stood 38 m above the ground. Only six columns from the south side of the temple and their entablature are still standing today. The back (west) wall of the temple podium contains three stone blocks each 19 m long (the so-called trilithon); two further such blocks remained in the quarry, unfinished. These are the largest architectural elements to have ever been used in ancient architecture. […] The nearly square courtyard in front of the temple measured 104 × 103 m and included two towerlike altars as well as water basins. Surrounding the courtyard on three sides were porticoes of monolithic columns made of smoothed, polished Egyptian red granite. Columns and veneer in costly coloured stones like granite, porphyry, and basalt were often used in Roman Imperial architecture to heighten the opulence of facades and interiors.