90 minutes to take visa, go through passport, pick luggage and get to domestic will be cutting it rather fine.

At a very empty time this is doable if there are no delays, if your plane docks at a gate (instead of parking away and the passengers brought by bus) and if there are not many other planes which have landed just before yours.

However, if both of your flights are on THY, they should try their best to get you on that plane or make up for it.

I think Pegasus does fly to Kayseri but not to Nevsehir. Both those airports serve the Cappadocia region with Nevsehir being about 30 minutes closer.

Both those hotels have good reviews on TA, but I do not like staying at touristy areas which are overcrowded in season and totally devoid of life after dinner out of season, so I would recommend that you stay at Nisantasi instead, an upscale area where many of our Jewish friends prefer to live, eat, drink and shop, and which has the best and most liberal mayor in Turkey. (His decorative theme for the streets was the nut cracker suite with toys everywhere and two stages for live music, in addition to the false snow, confetti and fire crackers on NYE.)

Thank you for your reply otherchelebi, I will check Pegusus about flying into Kayseri. It would be more comfortable to have a little bit more time between flights.

I've looked up Nisantasi on trip advisor and find 3 different listings. Were you suggesting House Hotel Nisantasi or Nisantasi Flats?

I welcome all other suggestions...

Either of those you mention are fine. Cheya Residence Nisantasi flat is excellent also. Park Hyatt is very good but rather expensive. location of Sofa hotel is also very good but I do not know the rooms or prices.

Check for Tesvikiye area also. This is just next to Nisantasi.
A possibly cheaper hotel is ParkSA Hilton about a ten minute walk from Nisantasi.

These areas have some of the best easily accesible cafes and restaurants that Istanbul has to offer in the Winter.