In the Android app "Minecraft Canary" there is a whole bunch of game info, essentially a game guide. One of the pages says "A single location on the map has been discovered to cause the most mobs to spawn. There are some tutorials on the internet which show how to find this location". It then says to build a huge tower which drags mobs into a grinder and drops the loot into your base.
I searched but couldn't find this info. Is it still relevant to the current version of Minecraft, and if so, where are these tutorials? I don't know how to find this mythical mob spawn, nor do I know about the tower trap it says to build there.
Best Answer
I believe this is referring to the zero chunk, or chunk 0, 0.
Note that since the Halloween update, the zero chunk can't be exploited as the most efficient spawn location, so you're better off just building a mob tower anywhere, rather than trying to find your zero chunk.
Minecraft Forum user Ruzhyo2000 posted a little tutorial on how to find your zero chunk.
Now, the second part of your question sounds like it's referring to a mob spawning tower. Different from the mob spawner block you find in dungeons, a mob spawning tower is basically a really dark set of rooms that, using currents of water, funnels mobs that spawn in it into into a single stream, kills them, and brings the items somewhere. See this answer on Gaming.SE for more info.