Have you read the replies above?

That pretty much covers it for Nagoya, one of the least interesting cities in Japan. "A nice place to live, but I wouldn't want to visit there."

However, it will be the lead-up to New Year's celebrations, so you can ask at your hotel if any of the local shrines or temples have any interesting events scheduled. I once visited some acquaintances there in September or October, and they took me to a festival where people write wishes on a slab of wood and then burn them in a big bonfire. Obviously, that won't be going on while you're there, but in any large city, there's always a festival somewhere.