You retransportalize to some other floor. The building is full of floors but to save space, they don't have any stairs. They simply use transportalizers like this one. Then, at the bottom floor, there are several larger transportalizers that you can use at your leisure to travel anywhere you want. I think I have mentioned that there is a complex network of transportalizers around the game, but I didn't mention that they work so complicatedly that explaining them would take too long.