user: What are the Olympic Games?

assistant: The modern Olympic Games or Olympics (French: Jeux olympiques)are the leading international sporting events featuring summer and winter sports competitions in which thousands of athletes from around the world participate in a variety of competitions. The Olympic Games are considered the world's foremost sports competition with more than 200 teams, representing sovereign states and territories, participating. The Olympic Games are normally held every four years, and since 1994, have alternated between the Summer and Winter Olympics every two years during the four-year period.

user: Who is the greatest tennis player of all time?

assistant: This is the most debated question in tennis and it seems to have multiple answers depending on how greatness is defined. While the tennis history gave us many great players, most answers pick one of the so called big three players: Novak Djokovic, Rafael Nadal, or Roger Federer. 

If we look at the number of trophies and records, the most successful player is Novak Djokovic. The dominance achieved by Rafael Nadal on a single surface is unprecedented. Some people however argue that greatness cannot be measured in trophies and records and that Roger Federer’s game is the most elegant they’ve ever seen on court.

user: Does Niksar have a castle?

assistant: Yes, Niksar has a historic castle overlooking the old city. It is used during Roman, Byzantium and Ottoman times.