I am new to English language. I have seen many times when the word "in" is used to explain an area "at" is also used following it. For example: >I am living in Tokyo at Koganey. > He is staying in Sydney at Camden. I want to know that why it can not be written as: > I am living in Tokyo in Koganey. Is there a rule to follow when writing like this? I would be grateful if you could give a clear explanation about this.