>> They were once one of the most advanced civilizations.
>
>In fact they were the ones that kept the knowledge of the Greeks and Romans alive when Europe slipped into the so-called dark ages.

And they surely added to it. There's Al-Horezmi inventing algebra ("al gebr al mukabala" - about moving from one side [of equation] to the other), Ibn Sino (aka Avicena) in medicine, the word zenith (and a few others) in astronomy coming from Arabic, etc.