I am going from BOS to IKA, from Dec. 23 to Jan. 4
That's a solid winter escape, Boston to Tehran (IKA, Imam Khomeini International Airport) over the holidays is a meaningful trip, and there's a lot to think through here.
First, the practical reality: routing from BOS to IKA is never a one-stop affair. You're almost certainly connecting through a hub in Europe or the Gulf, Istanbul, Dubai, Doha, or Frankfurt are your most common options. Turkish Airlines through Istanbul is historically one of the better-value carriers on this routing and offers solid business class if you want to make the long haul comfortable. Emirates through Dubai and Qatar through Doha are also very much in the mix, with the Gulf carriers offering excellent onboard product especially in business. Lufthansa through Frankfurt works too. Direct availability and pricing will vary considerably given the geopolitical complexity around Iran, so book sooner rather than later and make sure your documentation is fully in order before anything else.
On the timing, December 23 to January 4 puts you in Tehran for Christmas (which Iranians largely don't observe, so the city is normal and busy) and through to just after the Persian New Year run-up season begins. You'll miss Nowruz itself, which is in March, but January is genuinely one of the better times to visit: cooler temperatures make walking Tehran's streets and bazaars very pleasant, and the Alborz mountains just north of the city are snowcapped and beautiful. If skiing interests you, Dizin and Tochal are operating in January and are legitimately fun experiences, Dizin in particular is a proper mountain resort with runs that would surprise most Western visitors who've never considered Iran a ski destination.
Tehran itself rewards time. The National Museum of Iran and the Treasury of National Jewels are non-negotiable, the latter houses one of the most staggering collections of gems and crown jewels on earth, far more impressive than most people expect. The Grand Bazaar is immense and worth an extended wander. For eating, the city's traditional teahouses and kabab restaurants are where you want to spend your time, Moslem Restaurant in the bazaar area is an institution for abgoosht. If you have time outside Tehran, Kashan is a very manageable day trip or overnight and is one of the most beautiful historic cities in the country, with gorgeous traditional houses like Tabatabaei House that are genuinely world-class.
One thing worth flagging: Americans traveling to Iran face specific restrictions, U.S. passport holders are required to travel with a government-approved guide, and the logistics around visas and entry are particular. If this applies to you, make sure your tour operator or host situation is locked in before you finalize flights, as it shapes the entire structure of the trip. If you're traveling on another passport, the process is more straightforward. Either way, this is a destination that rewards careful planning and delivers something genuinely extraordinary for those who make it there.