If you've watched the TV spots and trailers for the new Total Recall movie, you've probably noticed a giant metal skyscraper-like elevator, that takes citizens from one side of the planet, to the other. Yes, this movie replaces Mars with an elevator through the center of the Earth, and it's a huge part of the movie.

But how do you actually create an elevator that goes through the middle of the planet? We asked director Len Wiseman, and he explained how it works, and why he wanted it in his movie.

A lot of the set reports have mentioned the giant set piece called the China Falls. What can you tell us about this?

It's called The Fall in the movie. Our film doesn't travel to Mars — that was a big difference between ours and the original. But I still wanted to make sure there was a sense of traveling, almost traveling to space, within our film. So we created this Fall. It's basically a 30-story subway system that travels through the core of the Earth to the other side.

It's the only way to travel to the other side of the planet — with air travel now being restricted because of many things that you'll find in the film. It's not safe and it's toxic [to travel around the world by other means]. So the only way to travel across is through the core. And when you do that you hit the center of the Earth, you hit a zero gravity moment. That gives you the sense of almost space travel. I wanted to give people the feel of traveling to a different universe, even though you were on the same planet. That was really the reasoning behind it. It was very complicated to put together. To put all the engineers and everybody together what would really happen if you took a 30-story building travel it through the center of the Earth, how would the people sit, and how would they rotate. Because when you travel to the other side of the planet, everything has to be reversed. But the actual machine stays the same.

Here's a little glimpse of The Fall that we snagged from the trailer.