The rMBP 2015 vent is at the laptop hinge. If you get the fans to spin up, you can feel the air traveling across the face of your screen with your hand.
That being said, it's still awful ventilation. I tried playing video games on it through Windows and Apple's drivers left the laptop more hot to the touch than I would like. I ended up using a fan curve controller application to fix that.
Yeah, I probably could have been more precise and said "there really isn't any ventilation" rather than "there isn't really vent". The vent is there, it's just completely ineffective.
That being said, it's still awful ventilation. I tried playing video games on it through Windows and Apple's drivers left the laptop more hot to the touch than I would like. I ended up using a fan curve controller application to fix that.