Black holes are gateways that take you to the Edge of the Universe. For some reason, no plant or fungus grow there. The air is dry, the water doesn't quench the thirst and doesn't even make things wet. The food can't be stored for too long, because even inside the fridge it spoils, and a deep fear of everything takes over anyone who spends too much time in this place. Whole cities are built, but are abandoned soon after their inauguration. Modern factories are opened and closed in just a few months, no matter how many clients they have. In short, it's impossible to inhabit this place before understanding and solving this problem.
Strangely, things like batteries, power cells and fuels are very durable there. A gas-powered machine can stay on for years. In some cases, the rust destroys the machine before it runs out of fuel.
The Edge of the Universe isn't exactly the limit of the universe, because the thin layer isn't visible or touchable from the inside and can only be reached through the black holes.
But, if we imagine the universe as a bubble, we'd be on the inside, and these black holes would take us to the thin layer on the outside.