Okay guys, I know it might sound crazy and maybe even a little dumb, but a bustrip to New York City and back in one day is really worth it!
Nina and me took the Megabus for 30 bugs roundtrip (http://megabus.com/) at 6 am from South Station and arrived in NYC at 10.30, a little tired but still excited for the next 8 hours in the city.
When we decided to to this trip, which was actually the night before, we primarily just wanted to visit the MOMA and see a special exhibition (http://www.moma.org/). So that´s what we did as soon as we arrived, but then Nina and me realised that we have lots of time left, so we made a nice little walk through Midtown and walked along the famous ice rink at Rockefeller Center, saw the amazing christmas decoration at Macy´s and had even time to enjoy crépes at the Public Library, where we could find a little christmas market.
We took the bus home at 7 pm, which was a little mess because the pick-up place for the busses was completely crowded and we had to fight for our places, but in the end everything worked out fine :-) So we arrived back in Boston at 11.30 at night, a little exhausted but super happy about our 18 hours trip to the greatest city in the world (after Boston of course)!