Which is the longest city in the world?

On the last day tea time, all the cousins sat together and were having fun with each other. Everyone was enjoying or sharing their experiences of life or some people were talking about their favorite books, songs, activities, or travel journeys. All of sudden my one cousin raised a question and that was Which is the longest city in the world? We all were blank on this topic and got confused. That's why I am here to know from you what is the actual answer to this question. So guys let's share here.

I want to know about day trips from san francisco.