As per my Polish fiancée:
For places to go, there's the new portion of Warsaw and the Old Town which is always pretty to walk through. You can find many restaurants in places like the Old Town Square where you can sit on a patio and enjoy some perogies and beer. There's lots of historical things to see such as:
- Warsaw Rising Museum
- The Copernicus Science Centre
- National Museum of Warsaw
- the Royal Castle
- Gestapo Headquarters Museum