I am sure Fantasia will have its own disco, most large hotels do. There isnt really much nightlife around the hotel area, its maybe 2 miles out of town....
In town you have Kaleici, the old town, with some bars and a couple of clubs there.
In centrum area there are bars, and then you have Bar St, where you have a great mix of bars there including irish, turkish and cabaret. It used to back in the day full of irish bars, there are still some, but now with renovations going on at the minute there is alot of work getting done there.