Black holes are fascinating objects predicted by Einstein's theory of general relativity. Though they were initially viewed as pathological and unphysical solutions, they were later understood to be a solid and generic outcome of the theory. They are objects where the distortion of space and time is so extreme that it defies imagination. Black holes give rise to paradoxes whose resolution requires us to modify our conception of spacetime. We will review how black holes went from being an apparently unphysical solutions to a central tool for discovering new perspectives on the nature of spacetime.