Created a new biome over the course of a week that spans across a large section of our already massive server map. Its features include, underground rivers, larger veins of resources, underground villages, and rainforests. To counter the high resource distribution we've added 'silverfish hives' large clusters of stone that hold hundreds of silverfish, in addition to this, the high cave ceilings and wide open spaces mean larger hordes of zombies and other mobs.
Screen shots don't give the new biome justice, check it out on foot at 108.60.137.125:25565 and hit the [underground] warp at spawn! See what you think

the silverfish hive schematic : The glass acts as a lure to player who doesn't know what the structure is, we've found that it almost always works, the glass leads the player into the hive and to the iron ore inside.. when the player needs to dig out, they'll need to break the hive open, and they'll find themselves swarmed. We'll be uploading the schematics in the next few days.

Additional Notes

Pictures