As the city of Troy was surrounded by high walls that could not be breached, a majority of the fights took place outside of Troy, many of which in or around the river Skamandros. In modern times, it is also known as the Karamenderes River, and during The Illiad it was also considered the home of a minor god of the same name. The river god was one of many that had gotten involved in the conflict, choosing Troy's side, that fought against other gods. 

Note: Google Maps does not actually pick up the river, but it does have a real world counterpart as mentioned within Turkey!