Beside the physical contrast, it can also be a contrast between subject matter; and that is how I feel about the image below.
To me the four main elements in the image all complement each other; the biggest contrast is probably the older Mosque against the ultra modern Burj Khalifa, the worlds largest building. The UAE flag links the two together and gives it a sense of place, while the fishing cages make for an interesting and authentic foreground.
In photography the rule of thirds is generally well understood, however another rule which is less known, is "the rule of odds"; an odd number of main subjects often looks more pleasing than an even number. This is just how our brain is wired I guess. I also like how the trio of the mosque, Burj Khalifa and UAE flag all have different sizes and play of each other.
Lastly, I envisioned the image as a square and therefore cropped it that way in post-processing.
Fujifilm X-T1 with the XF 50-140 f2.8 lens
ISO 200, 106mm (159mm full frame equivalent), f8, 1/420s
RAW file developed in Lightroom 5.7
More of my Architectural images shot in Dubai can be found here.
Remember, with regard to rules in photography, "Rules are there to be broken"!