Hagar Qim. Outer wall.
This is a closeup of the stone upright whose tip is visible in the previous photo. The stone seems tilted at an impossible angle. Why doesn't it tip over and crash? Sophisticated visual and engineering effects like this are found throughout the temples, often where one least expects them. The line of this stone beautifully defines the inward tilt of the temple wall, without any visible means of support.
Triangular "sockets," of uncertain purpose, have been carved into the base of the uprights, and also where two uprights join together. One such socket has been filled by a triangular stone, as seen near the center bottom of the photo. Another photo shows the best example of this construction.