What's the hole in the intake for....collecting antifreeze

Put a bottle of Water Wetter in the radiator and actually felt like it was running cooler in the engine well. Took it to Woodward Cruise tonight, and stopped after a stop-n-go trip of 6 miles. It was peeing everywhere. Got a rag out and it seemed like it was coming out of the hole in the intake (right in the middle of the pic). What's that for? Could antifreeze be coming out of there? thanks