During the portal storm, roughly a day into the whole ordeal, a large portal opened above the middle of St. Petersburg. What dropped from it, was a massive structure, larger than most have ever imagined a building to be. It destroyed a collection of buildings as it crashed into the ground, but managed to stand properly without falling over. Barely anyone had time to properly inspect it, but from what was seen at the time, the building appeared to be made by something sentient, considered by many as an artwork.
After the seven hour war, the combine began to send scientific branches to investigate this anomaly, having covered it with tests from top to bottom. As evident, even the combine is not aware of where this collection of metal has appeared from. A popular theory is that there's a third party somewhere in existance, and has accidentally been involved through the resonance cascade. Anyone who knows about this however may consider the lingering fear of the unknown, that there might even be something above the combine in the food chain.