The pillars of the Hypostyle Hall in Karnak, along with a view of architrave on top

There is a lot of speculation about how the roof of the pillars (known as the architrave) was constructed, since these were very heavy. What was the mechanism used to bring these heavy pieces (70 tonnes) to the top of the pillars ? There is no clarity on these items, with no conclusive proof available. In this photo, you can see a section of the pillars with roof on top (although most of the roof has fallen).
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