We took a day trip from Istanbul to Ephesus, the most famous ancient city in Turkey, by flying down in the morning and returning the same day in the evening.
It was a very convenient way of doing it for us as we only had a few days in Istanbul but this is somewhere we really wanted to visit as well.
Ephesus itself is only about 1 hours' drive away from Izmir airport and the flights take about an hour each way. We arranged it through a local tour company and found it very convenient as everything was included from the tour to flights and transfers. It was all very well organized so that we didn't find it too rushed or tiring, just as a very interesting day out.
You can see the day trip we did with them and some others here: www.toursistanbul.com/day-trips.htm
Even though it was just for a day, we found it very worthwhile and the city beautifully preserved.
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