John Kirhoffer: Most of the challenges this season are built into the landscape of Gabon. It's a unique landscape that we've never had before. These hills, valleys are great for running up, great for sliding down. We've got canyons that we're building inside of. We've got lakes. We've got streams.

Our first Immunity Challenge is big and bad. In keeping with Earth's Last Eden, this is temptation valley. There are 9 players in each tribe and 6 of them are tied together. They're wearing belts with ropes in between them. They race through this obstacle course. They come running down the hill, charge through the swamp. They come up and over a tall A-frame then they start charging up a hill, 150 yards up a hill. They crawl under a set of fence posts, over, under, over again. Then they charge up to the dig area where they will dig three bags of puzzle pieces. Down to a gate. They have to dig under the gate, all 6 pieces pieces [bags] and the players under. Pass the puzzle pieces off to the three remaining players who will then have to assemble a long puzzle of their tribe's flag (?)

Find out which tribes (Fang and Kota) the Survivors will be on before the season premiere!

Exclusive: The cast of 'Survivor' Gabon

-- written by Dalton Ross

The 18 contestants competing this fall on Survivor: Gabon-Earth's Last Eden for the series' 17th cycle include an Olympic gold medalist, a Gilmore Girls actress, and a professional video game champion, EW.com has learned exclusively. Crystal Cox, who won gold at the Athens Games in 2004 as part of the 4x400m track relay team, is the biggest name on the roster this season, which premieres with a two-hour episode on Sept. 25. Also among the fresh faces is Jessica "Sugar" Kiper (Gilmore Girls fans may remember her as the pin-up model who made out with Milo Ventimiglia during her four-episode arc as Shane) and Ken Hoang, the current international champion of Nintendo's Super Smash Brothers Melee video game. There will also be a prominent international presence, with contestants who have lived in South Africa ( Gillian Larson), London (Ace Gordon), and Chile (Paloma Soto-Castillo).

As for the format, the biggest twist of Survivor: Gabon involves Exile (formerly Exile Island). "When you go to Exile this time you can either get a clue that will help you find the hidden immunity idol, or you can get 'instant comfort' - a nice thing to sleep on, some food, some fruit," explains host Jeff Probst. "Depending upon the time, we'll make the temptation bigger and bigger. The idea was to see if anybody would be dumb enough to choose comfort over the only thing that guarantees you to stick in the game, which is immunity." Okay, did it work? "By the time this season is over, you can make the case that maybe this is the dumbest team when it comes to idol play."

Also for the first time ever, Survivor: Gabon will be shot entirely in HD. "If you're a Survivor fan and you have HD, it will be a completely different show," Probst promises. "When you incorporate the wildlife, it's kind of like being in a Spielberg movie. I mean, it's so real-looking that it's exciting and scary." And that wildlife Probst speaks of will come into play when elephants visit a tribe camp. "A truly real, raw moment of a wild animal that's not in a park or some protected area," Probst says.

The contestants of Survivor: Gabon will be divided up into two tribes at the very outset by a good old fashioned schoolyard pick 'em, which will immediately lead to the contestants' first challenge. And while there are no hardcore "showmances" this time around, Probst does tease that one player proves particularly popular: "Marcus, the doctor from Georgia - one of the most arrogant guys that we've had on the show - he at one point had three people after him. And not only women."