Reflections are a great way to make composition (and whole image) more interesting. You can use them to add symmetry to your image for instance. Sometimes you can make them look like a portal to another parallel reality.
In case of this photo of Torres Colon in Plaze de Colon in Madrid I found this puddle in the shadow of a tree and decided to fill it with reflection of the Torres Colon skyscraper built in the 1970’s. Thanks to the reflection, the image looks quite nice. Without it it would be pretty boring.
Camera: Canon 5D MK II
Lens: Canon 24-105 f/4 L IS USM
Focal length: 24 mm
Exposure time: 1/160 s (“middle” exposure)
Number of exposures: 3
E.V. Step: 2
Flash used: no
Filters: circular polarizing filter
Software: Magic Lantern 2.3, Lightroom 4.2, Photoshop CS6