The concave cavities generate an air cushion upon contact with water droplets, functioning much like a spring to prevent ...

The inner surface of the sculpture flips the world upside down, an optical effect that occurs when a concave reflection is viewed from beyond its focal point.

Both dials use the shape of a concave hemisphere, a shape like the inside of a bowl that mimics ... The hemispherium was carved out of a block of stone and its inner surface scored with eleven lines, ...