Ireland, Italy, Turkey Itinerary

First you should give some key details, such as how many days you plan on being in each place and what your interests are. Also, what cities you are planning to fly into (and out of) and what attractions do you want to see in each place? Right now, your question is too general. Going to 3 countries that are not close together in 15 days seems like a lot.

I am staying for 2 weeks. Probably 3 days in Ireland, a week in Italy (arriving in Rome) last 4 days in Turkey (arriving and departing from Istanbul.

I would recommend staying all 4 days in Istanbul - there is plenty to do there (Topkapi Palace, Haghia Sophia, etc). You really don't have enough time to go anywhere else in Turkey without losing more travel time. And, fortunately, Istanbul has a lot of indoor attractions in case the weather is sour. I doubt you'll see many tourists in January - during tourist season, Istanbul is very vibrant and full of tourists. Check out these websites to get you started. Send me a private message if you need hotel recommendations (most of the tourist sites are in an area called Old City, or "Sultanahmet").

http://travel.nationalgeographic.com/travel/city-guides/istanbul-turkey/
http://www.turkeytravelplanner.com/go/Istanbul/
http://www.lonelyplanet.com/turkey/istanbul/things-to-do/top-things-to-do-in-istanbul

I'll leave it to others to advise you on Ireland and Italy, but those are my two cents on Turkey.

That puts you in Italy over Christmas. You have several airport options from Dublin and to Istanbul. Where to spend a week in Italy depends on what you want to see and do, and what's practical around Christmas (when most sights and many restaurants are closed). I suggest you tell us what draws you to Italy and what you're must-sees and must-dos are. With a week or less, you can possibly see 3 cities whirlwind or 2 at a more reasonable pace - again, with the caveat that Christmas may make it difficult, especially for 3 cities. Or you could pick one city and see it in depth, with day trips to surrounding towns and sights.

Check out Turkish airlines for flights between Italy and Istandbul. I used them between Rome and Istanbul and it was excellent.

I would also recommend reserving a tour of the Vatican ahead of time through their website.

Thank-you for the information so far.