Exploring Hyrule in the Legend of Zelda, the Wind Waker
Notice anything odd about where Link is fighting this keese enemy?
Well if you do, and wanted to know why the area looks so different and there wasn't much detail there, it's because Link is fighting the monster in Hyrule. And what's more, this is outside the boundary of the area you can normally explore AND he's fighting an enemy there, which seems impossible.
But here's how to do this feat, and other things I've found relating to this:
First, you have to go under the archway with the keese (bat) so it comes down to attack. Now use the moon jump to levitate over to where the wall near the Dark Nut is, and float so you go quite high into the air. You should, at a certain height, scale the wall and land on solid ground. Then, you just wait. If you did this right, the keese should have followed you through the invisible boundary! They act like normal and will follow you around the whole area. If you kill them, the treasure drops on the ground as normal as well.
To fight a chuchu past that boundary, just go near one but outside the boundary and hookshot it. You will bring it past the wall and to where Link is standing, causing something like this:
If you get the monster near the high arch way (with the roof and tower), you can go underneath the path to an extent. Then, use the hookshot on the creature and it will fly like 50 foot into the air, right over the boundary. The walls here aren't solid, so both you and the enemy will just pass right through them.
You can also manage to get a Peahat to follow you outside of the normal game area sometimes.
So what's the area actually like? Well, all ground near the road is perfectly solid, this occurs until you get a large distance from the path. Then, the ground is non-existent from then on, and you will fall for ages if you try to walk on the 'land'. Any trees, rocks, pillars/statues, grass, plants and walls outside of the normal area are possible to go through just by walking right at the object.
Oddly, the more 'intelligent' enemies don't know where you are! You can walk right above a Moblin and it will be totally oblivious to your hidden presence, just use the weapons and you cause some odd reactions! Same with the dark nut too, even on top of the wall, sword distance from the knight, it just walks around oblivious to you being two inches in front of it's nose!
Do not go between the grass bank and the wall by Hyrule arch, or you will be stuck in a never-ending sliding position. The roof of many buildings are only solid at the very sides, so going through the middle of the castle roof will kill you. If you fall through at the right angle, you are warped inside the actual castle.
Never the less, just enjoy yourself? This area was never intended to be walked on, so don't think it's a glitch it's not solid. To test out whether the ground is solid, just throw or bomb or shoot an arrow where you go. If the bomb lands on the arrow gets stuck in the ground, that area is solid ground. If it disappears, go in the other direction.