The 1961 Impala is often referred to as a bubble top car, and when you look closely at the styling, it's not hard to see why. The A-pillars that flank the windshield have a distinct curvature, giving the impression that the front of the greenhouse is bowed outward.
Then there's the large back glass, which incorporates thin and heavily-sloped C-pillars. On the sides of the car, the frameless windows can be rolled down to reveal no central B-pillar, completing the smooth bubble appearance.