The girls

Written by Icelandic composer Jón Leifs in 1964, the piece called Hekla, Op 52, requires four sets of rocks hit with hammers, steel plates, anvils, sirens, cannons and metal chains to play.

From the 700s to the 1200s, Baghdad was an Intellectual Center unrivaled in the world. It's House of Wisdom studied mathematics, astronomy, medicine, alchemy and chemistry, zoology, and geography.