Pokemon Twilight Cheats :
Code - Hidden/Secret Areas!
Yup, they're hidden alright!
1. On Route 11, while surfing there is a gap upward toward the end section of the route toward the top barrier. From there you can sneak through to challenge a trainer and find an island with several secret base sections, and another small gap to more secret bases! (Also, on the larger area with secret bases, head toward the top left - you should be able to walk through the barrier and come up the cliff there, then loop around to a sign that says: "Cheater")
Secret: (need secret power)
1. There is a sign that leads to this area in Route 1. It reads: "The secret lies between the mossy tree and the immediate flower". All you have to do is head back to Mossville and use secret power on the flower in the uppermost part of the town! From there, you'll reach a large, flowered area!
2. On Route 2, surf off the bridge going up. Then, there is a tree to the topright which will unlock an area that needs the move cut to get into the grass! It has been hinted as the "Starter Grass" where you'll find the Ayenn Region Starters!
3. Right when you enter Route 5, you may use secret power on the bottom trees to reveal a windy path to a lakebed, from there you can surf to beat an old man trainer with a shiny Urich! There is also TM 99: Lazer as well!
4. At the end of Route 11, right before entering the Clear Lake town, you are able to use secret power on the bottom trees to open a path to an odd colored green tree! A large area of grass lies behind it!
5. There is also a nice little secret area hosting some new pokemon in the 3rd Gym in Russet City! Head to the white statue/thing at the top of the Gym - however, you will need a Lvl. 50 pokemon to access it!
6. Finally, I found the secret desert called Pikara Desert! All the way in Russet City, navigate your way to the right side of the city. From there, a section of fencing can be broken using secret power. Head down the newly opened path to reach an empty house. There, use secret power on the upper plant to open a ladder leading to a tunnel. After some traveling down the tunnel, you should reach the Pikara Desert! Although it apparently isn't finished yet so you can't find any pokemon and a barrier won't let you explore much of the area.
Any other secret or hidden area location? Do Share! :D