how are they not limitless?
The further you go, the fewer decimal places you have. Torque only handles 6 digits.
You go to X 4000, you only get 4xxx.xx. You go to X 400000, you only get 4xxxxx, you go to X 40000000, you only get 4xxxxx00
Besides, even if it were limitless, it's the same thing over and over again. Whenever I'm on a server that just uses a wide stretch of looping terrain I actually navigate myself by how many times I've seen that same hill.
Close it off by having mountains too high for the player to scale, or other impassable features like limiting how long they can swim.