Complex sentence: The idea that it constitutes an ancient artificial edifice was publicised by Houston-based expatriate Bosnian author Semir Osmanagić, but scientific investigations conclude that it is a natural geological formation known as a flatiron.
Split into simpler sentences: The idea that it constitutes an ancient artificial edifice was publicised by Houston-based expatriate Bosnian author Semir Osmanagić. They claim it to be a natural geological formation known as a flatiron.