This photos exemplifies symmetry. The two bridges are perfectly balanced in the frame as well as their reflections. There is enough space in between and on the sides of the bridges that it makes the bridges look enormous.

This photo is completely unbalanced. The house on the right as a lot of optical weight and makes you focus solely on the house. There is a lot of space everywhere else around the house which gives the home a very isolated feel. 

In this photo, a brick wall and a bike are split perfectly in half. The photo is completely symmetrical. The drain pipe in the middle splits the frame in half and makes you focus on the bike. There isn't a whole lot of space due to the fact it's shot up against a wall. It has a narrower depth of field than the other photos.