The High Command Heart Building is a skyscraper located in the outskirts of Moscow, Russia and an easter egg in the Epsilon mission The Conqueror.
When the High Command Heart Building is destroyed, a Wolfhound emerges from the rubble, causing the EVA to quickly tell the Proselyte to shoot it down before realising that it is not relevant to the game's plot.
The High Command Heart Building and the Wolfhound are references to the Red Alert 3 mission Crumble Kremlin Crumble. The Kremlin's Heart appears in that mission, where it must be destroyed by the player-controlled Empire forces, at which point a Twinblade helicopter will fly out, carrying Russian Premier Cherdenko and his prized Time Machine, before being shot down by Empire forces as well.
The High Command Heart Building is based on the Palace of the Soviets, a building that was supposed to be the center of the Soviet government but was never built.