Battle Towers can be found all through out the world and all the generated dimensions, including DivineRPG Dimensions. They are common and can easily be found useing Rei's minimap. Inside are different types of spawners, usually zombie and spider, but cave spider, skeleton, and even creeper spawners can appear. The tower consists of floors, with a double chest protected by two spawners. The higher you go in the tower, the better the loot (you can even get chainmail armour, which is alot better than iron and even diamonds because of DivineRPG). There are also holes in the floor making it so you or mobs can fall through.
At the top of every battle tower is a boss. The boss will fire ghast fireballs at you and will attempt to bash your brains in. He has 150 health, which isn't much, since most of the DivineRPG mobs have well over 200. He drops diamonds and clay, and occasionally a piece of paper. After you defeat the boss, the tower will begin to fall apart, so you better start running!
Early in the game, running into these towers is a good idea, since you'll get tons of XP, and since every few XP levels, you get your health refilled and an extra heart, you can keep going. Don't go all the way to the top until you feel prepared to fight the boss, though. Death isn't fun.