A Dyson sphere around a black hole
The whole concept of a Dyson sphere is kinda idiotic.  Any civilization that is capable to build one, it is probably able to work out fusion energy very efficiently.<p>There is no point to go and harness energy around a star or a black hole, when you can just produce it locally with a lot less resources&#x2F;waste and materials.  The sun itself is actually very inefficient in producing energy.<p>There is no need to harness the sun million of km away,  when you can recreate it in your home planet. The only way to produce a dyson like of sphere, is to tame an over-heated sun, and reflect away un-needed energy.  But there is no point to build one to just harness it.<p>It makes great sci-fi stories, but that&#x27;s about it. Scientifically, it just doesn&#x27;t make sense.