Advanced civilizations could be using Dyson spheres to collect energy from black holes

Black holes are more than just massive objects that swallow everything around them—they're also one of the universe's biggest and most stable energy sources. That would make them invaluable to the type of civilization that needs huge amounts of power, such as a Type II Kardashev civilization. But to harness all of that power, the civilization would have to encircle the entire black hole with something that could capture the power it is emitting.