Karnak was built and expanded over 2,000 years by successive pharaohs from the Middle Kingdom through the Ptolemaic period (c. 2055 BC–30 BC). The famous 'helicopter hieroglyphs' at the Seti I temple are the result of palimpsest — later plaster and carvings layered over original texts, creating ambiguous overlapping shapes when the plaster erodes. Egyptologists have documented the construction process through administrative papyri, workers' marks, and quarry records.