Pokémon Diamond and Pearl/Fuego Ironworks

There's not much reason to go here except for items, though the items you can nab are pretty good. Now, the basics of the place are this: you can only reach it by water, for one, so you'll need HM03 Surf to reach it. Once you're inside, you'll notice that the only way you can get anywhere is to use the tiles on the floor, which spin you in the direction labeled on them until you hit a wall or another tile. You'll meet a few trainers along the way, most of which have Pokémon in their low twenties. Eventually you'll reach the end, where the boss of the ironworks gives you a Fire Stone, your second one assuming you picked the other one up along the way.

Items

 * Fire Stone:X2
 * Burn Heal
 * TM35:Flamethrower