From WoWWiki

Blackrock Stronghold is a massive fortress controlled by Blackrock Orcs. The stronghold is located in the northern region of the Burning Steppes, just outside Blackrock Spire.

Subzones of Burning Steppes
Altar of Storms • Blackrock Mountain • Blackrock Pass • Blackrock Stronghold • Draco'dar • Dreadmaul Rock • Flame Crest • Morgan's Vigil • The Pillar of Ash • Ruins of Thaurissan • Slither Rock • Terror Wing Path