Empires, the award winning Half-Life 2 mod, combines the best of the first person shooter and real-time strategy genres. Fight as either the Northern Faction, remnants of the fallen nation of Jekotia, or as the imperial Brenodi Empire. Empires features:
Dragon's teeth were added after the second flag to help slow BE tank movement and prevent them from falling into the hole. Once the bridge over the hole has been built, the dragon's teeth retract, allowing tanks to proceed.
So much for driving tanks up there, good idea