Swarming Pillar
The Swarming Pillar was a large silithid-infested peak in the middle of Silithus containing one of their hives, just south of Cenarion Hold. It got its name from a massive swarm of small silithid that buzzed around the hive.
The silithid hive was eventually destroyed at the end of the third invasion of the Burning Legion when Sargeras tried to destroy Azeroth through Silithus.
Notes
The rocks and hive together resemble a zerg hatchery from StarCraft.