Street lights at night can be very pretty. For someone who lives close to the centre of a large city, skirting round the edge of the town centre can provide a host of beautiful views at night.
A more subtle example, of course, is in the picture of the day at the top of this post. The lights cluster around the top of the leaves like fireflies, obviously part of a cityscape but at the same time abstract.
I'm not 100% happy with these, but they're not bad considering it was raining and cold and very late at night. Maybe I'll have to get the tripod out, drop the aperture to f16 or f22 and take some long, detailed exposures of Sheffield at night.