Black holes are one of the most fascinating objects in Nature, so much so that they often feature in science fiction movies! But, why is that we find them so interesting? In this talk I will explain what is our current understanding of black holes in General Relativity, Einstein’s theory of gravity. As we shall see, black holes are extremely simple objects and yet they encode some of the greatest mysteries of gravity. Their “blackness” makes them very hard to see, but as I will explain, in the near future we may be able to “hear” them. It turns out that the interest in black holes goes beyond their traditional playground in astrophysics. According to recent developments, black holes encode properties of theories of particles, fluids (and turbulence) and superconductors!