Several years ago I met a Production Assistant who worked on RAIDERS OF THE LOST ARK and was told an interesting story: that SECRET OF THE INCAS was indeed the inspiration for RAIDERS... but it went much further than that. The PA stated that George Lucas had seen SECRET years before and adapted the story into his own vision for Indiana Jones. Lucas screened SECRET -in secret- for Spielberg who immediately attached himself to the project. Here's where it gets interesting: Spielberg quickly negotiated the rights to SECRET and the contract demanded it be shelved and never released in the United States so there couldn't be any direct comparisons to RAIDERS. That's why even today you can't buy an official NTSC copy of SECRET; my region-free disc came from the U.K.! And the similarities between Heston's costume and Harrison Ford's some 30 years later were no accident, either: the PA told me that the RAIDERS creative staff were required to watch SECRET and use it as source material as much as possible to save production time/expense. And, it's clear they took a lot of notes! Others have mentioned the obvious similarities, but there's another really quick one that most people overlook: it's a little musical phrase on the SECRET soundtrack that is identical to one that John Williams used later on when he scored RAIDERS. Listen closely and it'll jump right out at you. Another coincidence? I'm not so sure! Further, Charlton Heston was famous for talking about his filmmaking experiences, yet he never directly -or publicly- mentioned SECRET... not even in his detailed autobiography, "In The Arena". He would only say that he once made a film high in the Andes where it was very difficult to breathe! Privately he allegedly had plenty to say: that he was contractually prohibited from mentioning his work on SECRET and that he seriously resented the fact that Spielberg had so thoroughly usurped his character and with little alteration turned it into the cult-status-cash-cow that Harrison Ford's Indiana Jones attained.