From WoWWiki

Terrorweb Tunnel is a long and winding tunnel into the mountain northwest of Terrordale. It is full of Crypt Fiends (Nerubians), and stretches through the mountain from Terrordale in the north and extends south to the spring of the Thondroril River. At the entrance from the river, you can find a level 61 (elite) quest giver, Tirion Fordring.

One must be very careful when travelling this path, as not only is this path crowded with many Crypt Fiends, but occasionally a very powerful and elite member of its kind, the Nerubian Overseer, stalks the tunnel.

Terrorweb Tunnel, Thondroril entrance

Terrorweb Tunnel, Terrordale entrance

Subzones of Eastern Plaguelands

Blackwood Lake • Browman Mill • Corin's Crossing • Crown Guard Tower • Darrowshire • Eastwall Gate • Eastwall Tower • The Fungal Vale • Hall of Arms • The Infectis Scar • Lake Mereldar • Library Wing • Light's Hope Chapel • Main Hall • The Marris Stead • Mazra'Alor • Northdale • Northpass Tower • The Noxious Glade • The Pestilent Scar • Plaguewood • Quel'Lithien Lodge • Scarlet Base Camp • The Scarlet Basilica • Stratholme • Terrordale • Terrorweb Tunnel • Thondroril River • Tyr's Hand • Tyr's Hand Abbey • The Undercroft • Zul'Mashar