There wasn't a particularly good chance of keeping this whole venture a secret for very long, but Tony still quietly charmed his way into the bowels of the Hunter Sportsplex, promising a generous donation if someone would be so kind as to give him a tour and thorough lesson on its interaction and alignment with the city's greater infrastructure. It was all very illuminating and worth the several grand, honestly, and kept Iron Man from slipping most noticeably into a manhole above ground, perhaps not just once. It was, he realized, between its spacious hallways and vaulted myriad of rooms, uniquely suited and a number of disasters and not yet tested in such emergency situations. He'd send his sketch up of the interior maps to the Avengers-- well. He'd hang onto them, for future reference.
Left alone, ostensibly to inspect the tennis courts and watch a deep booming match between a pair of competitive sorority sisters (all right, that might have gone on longer than it needed to), Tony took his chance to sidle casually off toward the STAFF ONLY, DO NOT ENTER, and other such enchanting signage in the greatest (human) inhabited depths of New York City. The Sportsplex didn't quite reach the outer edge of the pulse's impact, safely outside of the gamma signature and any accidental Tennis Hulking. That would have been an interesting match, though. It was dangerously close enough and even if that faint energy spike wasn't the lost Cosmic Cube, Tony thought someone should investigate before the spread of its impact got any wider. Hammer could hear the details later, once the problem was contained.
Iron Man's boots echoed heavily in the concrete as he invited himself into the darkened sewer system. Every 40 feet, a bare bulb illuminated a small, moist patch of the narrow lip of the tunnel, enough for Tony to see the bacteria swarming and conjugating. The suit was sealed tight and dedicating power to life support systems well before he was within range of the pulse. There wasn't any outward shift. Slimy hallways went on, darkness in the distance, the continuous sound of running water making Tony regret the third cup of coffee. Only the readings on his screen revealed the energy signature.