In big, open rooms, sounds can bounce around, making it hard to hear music clearly. So concert halls need to be designed to stop echoes. In the music room of an ancient palace called Ali Qapu, in Iran, the answer is hundreds of intricately shaped holes. The ornate cut-outs absorb sound with each one catching and absorbing a range of sound waves according to its shape. These kinds of holes are called Helmholtz Resonators and today, architects include similar holes in concert halls and recording studios.