Hey, uh, could sombody tell me how to get to that patch of land to the..

You must have a National Dex in order to even think of going there. Before the National Dex, a man will block an alternatave exit. When you have the Dex, he will be gone. Take Defog and follow the Maze out to the exit. That should take you to the patch of land known as Route 224.

You have to get the National Pokedex. Then go to the cave entrance of the cave where the man was blocking the entrance. Go through the rest of the cave, and you are there.

First of all, you need to beat the E4 and obtain the National Dex. Once you do, fly to the Pokemon League HQ and go down the waterfall and in Victory Road. Go down and across the bridge, go down the wall using Rock Climb, be sure to not fall down the ledge >.< continue upward until you see an old man, go up the stairs immediately past him, and across the bridge and keep going east and you'll reach a cave. Go in the cave and down the stairs, and use Defog. Help the girl get through to the end, and exit the cave following her. You'll end up on Route 224, a "miniature of Sinnoh".

Right now, it doesn't serve much purpose except for a little training and money. But, if you obtain the "Oak's Letter" by cheating or going to a Nintendo Event when they come out, a route will be extended from the end of Route 224 that leads to Flower Paradise. A level 30 Shaymin can be found here UNDER THOSE CIRCUMSTANCES!