In two areas of Saudi Arabia, hundreds of prehistoric formations that look like large keyholes are piled up. For long stretches, they can be seen to the right and left of narrow gullies that might once have been watercourses. Perhaps it was simply a lack of space here that caused circles and triangles to grow together to form these strange keyholes. It is a pity that nothing more is known about this archaeologically.
(Geografical coordinates below the pictures.)
Images courtesy of Google Earth™
These pictures are only a small selection. All the objects I found are included in the following download (Google Earth required): Download Google Earth KMZ >