Extreme XP Maker

This spawner gets you tons of XP.

Step 1: Gather Materials

Get water, lava, flint and steel, mob spawning stone, and obsidian.

Step 2: Base

Make a 3 by 10 row of mob stone and hollow out the middle 1 block deep and fill with water, and at the last block deepen one more block and fill with lava. Then surround with obsidian.

Step 3: Portals

Make portals around the structure.

Step 4: Wall

Add 2 more obsidian layers around the structure and build up the last layer.

Step 5: Lava

Put lava in between portals and wall.

Step 6: Extra Layers

build portals on top of each other as many times as you want (more layers better effect).

Step 7:

Build a portal in the middle.

Step 8: Stone and Water

On top of the portals build a stone layer in between. Then build 2 high wall of obsidian. After you put water so it flows inward.

Step 9: You're Done!