This is an entry to http://ceenphotography.com/2016/03/23/cees-compose-yourself-photo-challenge-19-geometry-in-photography/ .
Cee is right: after a while you see geometric figures almost everywhere. To start off, here are some obvious choices, all from the same church in Mönchengladbach, Germany:
The geometric forms are obvious and don’t need further explanations.
From man-made, manageable shapes to the grandiosity of nature. Many mountains are pyramid-shaped which is rendered as a triangle in two-dimensional space:

And from the same corner of the earth, the Berner Oberland in Switzerland, the unmistakable triangle of the Eiger, overwhelming, breathtaking, and just plain HUGE:


I seem to have a propensity to triangles as the following photos show quite clearly (all taken at the Rugby World Championship last autumn, in Newcastle, South Africa playing Scotland). Whether it’s a group of players:
or individuals:
I found one without a triangle, though:
And just to end up with something completely different: