We're planning to go to Rome the week before Christmas for 3 nights. The Vatican is a must for me, as is the Trevi Fountain. Is there anything not so obvious that you would say is a must see? Also... any recommendations for a hotel please? We've got a budget of around £100 left for the hotel for 2 adults and a small baby, and want to be positioned as conveniently as possible. thank you!
It is a little over your budget, but we stayed in Hotel Mascagni - www.mascagnihotelrome.it - which is near the main Termini station, and it was very nice. We could easily walk everywhere from there. Our favourite thing about being there was wandering around, seeing what popped up around the corner. Someone else might suggest something more central though - that's the only hotel I have stayed in there, so I don't know! Apart from the Vatican and the Trevi fountain, there are of course the Spanish Steps (although I didn't particularly understand the fuss about those) and if you are not too creeped out by the idea, the Capuchin crypt is pretty amazing - en.wikipedia.org/wiki/Capuchin_Crypt
Rome is very accessible - we stayed at Hotel Santa Maria in Trastevere - it is truly fantastic, especially for families. It is across the river from Trevi but on the same side as the Vatican. Have a look on Trip Advisor as there is a huge range of hotels there.
Definitely visit the Christmas market in Piazza Navona, preferably by night with the lights on. Lots of traditional cribs and accessories for sale as well as Befana dolls (a little witch that brings presents to children on the 6th January), chocs and sweets and a traditional merry-go-round. The Pantheon is the most amazing building in Rome. Hotels near the station are convenient for buses but Trastevere area is better for walking around and less traffic. There is a shuttle bus from Trastevere up the hill to Gianicolo where you can see the whole city below you. Campidoglio for the best views across forum to colosseum and lovely in itself.
If you like Christmassy things take an evening trip around the city on one of the open top buses to see the Christmas lights - we live near Rome and take DS and his friends every year, you will see them of course just walking around but its good to sit on the bus, rest your feet, and see everything that way. Also, for a really nice Christmas display and decorations go to Vertucci, via della Croce, if you want any Italian Christmas decorations they have some lovely things - the area is also quite nice to wander round, with Christmas lights and cobbled streets, lots of small shops with Christmas lights and displays (bit packed on Saturday though). Have a good trip.