Death Zone

The Death Zone was a large section of Gallifrey. It was used in the days before Rassilon by the first Time Lords, who had immense power. They used a device called the time scoop to pull beings out of time and place them in the Death Zone, where they would play the Game, sometimes referred to as the Game of Rassilon, although he, according to history, is the one who put a stop to the Games.

The Death Zone was comprised of various different terrains which allowed different species to survive. There were mountains, marshes and one road. The fog was thick so one couldn't see where one was going and it was difficult to see the red thunderbolts that fell from the sky. (DW: The Five Doctors)