In The Thirteenth Floor, protagonist Douglas, top guy in a company that builds inhabitable computer-based realities, comes to suspect that he himself might be a virtual character in a virtual reality. He confirms this suspicion by driving out of the city. He just keeps going until the road gets worse and is eventually blocked off. He smashes through barricades and arrives at the outer edge of the simulation where the physical world devolves into green wireframe like a coloring-book that has yet to be filled in. It must be very shocking to learn that your reality is not real, but I assume you already know that; you’re here because you too have made that drive.