Use this phrase to emphasize the negative visual aspect of a scene or object. The graffiti-covered walls were not a pretty sight.
Pro Tip 2/3
Emotional Response
It can evoke feelings of disgust or disappointment upon seeing something. Seeing the littered beach was not a pretty sight.
Pro Tip 3/3
Beyond Physical
Although often about appearance, it can also refer to situations that are chaotic or problematic. Financial reports full of losses are not a pretty sight.