Minecraft wiki entry for Spawner_traps, associated text: This trap is highly recommended. It's effective and safe on all mobs, except blazes, since you need water. Disable the spawner, and then make a 10×10 room around the spawner. On one side, place water on every block. On the opposite side, make a one-block deep trench extending along the side opposite the water. Light up the trench well. The holes have to be next to water. Now, get plenty of food, a few chests, and two or three swords. Remove the torches and let mobs spawn. The water will bring them to you, and you can shoot them and hit them. Also, make a room to eat and heal in safety, just in case you didn't build the trap thoroughly. With this trap, you can go for hours in one go, and gain a massive amount of experience levels and items at minimum risk. The trap system is built in a way where you can easily leave when you want, with almost no creepers or non-spawner mobs popping up.