Underground Jungle

The Underground Jungle is one of the more difficult areas you can find in the world of Terraria so far. It can be found close to surface or deep underground. It is suggested that you should dig downwards on either side of your map and continue digging horizontally to the opposite direction if you want to find the Underground Jungle.

The Underground Jungle is huge and takes a long time to fully explore. Shrines are exceptionally common in this environment, often containing chests with rare items or weapons that you can't find anywhere else. You can also gather materials that can be used to create rare items.

Hunting the Jungle
An efficient way to find an Underground Jungle is to get a Depth Meter, travel to the farthest point on your map that is opposite your Dungeon and depending on your map size, dig down to the appropriate depth, and start digging towards the opposite side. This can take a lot of time but it's guaranteed that you'll find one.

Keep in mind, that it might be deeper on your world, but these are general numbers.

With the 1.0.4 update, you can now find the Underground Jungle by finding the Surface Jungle and digging down.

Monsters inside the Underground Jungle

 * Hornet
 * Man Eater
 * Jungle Bat
 * Piranha

Items in the Jungle

 * Anklet of the Wind
 * Feral Claws
 * Nature's Gift
 * Staff of Regrowth
 * Jungle Armor (as drops from the Hornet and Man Eater)

Unique Material Drops in the Jungle

 * Jungle Rose
 * Stinger
 * Vine
 * Jungle Grass Seeds