Albert Einstein's General Relativity will turn 100 years in 2015, but does not feel its age. In fact, it is still in excellent agreement with all the available observations of our Universe, from the solar system to the most distant galaxies. The two single most surprising (and largely untested) predictions of General Relativity are the existence of gravitational waves and black holes, and both will be tested in the next few years with high-precision laser-interferometry experiments.
In this talk, I will review the basics of the theory of black holes and gravitational waves, and show that upcoming experiments will not only verify their existence and nature, but also open a whole new window on our Universe. For instance, they will allow us to \"listen to the echo\" of the birth of galaxies, to measure strong-gravity effects such as the dynamical nature of spacetime around rotating objects, and more in general probe astrophysics, cosmology and fundamental physics with unprecedented accuracy.