Originally Posted by
KenJohn
The
IST airport hotel is fine if a little clinical and functional. It is better than spending the nice in a lounge with a proper bed, shower and bath. Also a restaurant for breakfast and other meals. Cannot remember if they do room service. Its not very busy from recollection
The hotel is is two parts - one airside and one landside and is part the terminal itself. If landside, one has to walk outside the terminal right along the side and down the hill to access the hotel - found it a little confusing my first time there.
Just remember that if you are a UK or US passport holder, you have to pay for a visa on arrival at a separate desk before heading to immigration if you have to go landside.
Only £10/$20 for the visa, though, for those nationalities. Given that the airport hotel is not especially cheap, your lira is likely to go further landside in terms of accommodation. Since the OP's flight is not until 1pm the next day, I would personally go into town, if only to have a little walk around the old town the next morning.
From the OP's other question about closure time of customs, however, I think that his intention, as
David-A suggested, was to use the BA lounge as an arrival lounge before heading into town to sleep for the night.