Hi there - we went to warsaw a couple of years ago.
The old town is fascinating, beautiful architecture - especially the old town square - and an amazing tribute to regeneration - try and get some pictures of the destruction caused during WWII in order to compare it with the reconstructed old town of today.
The Royal Palace is really interesting with some lovely art, objects and tapestries
The National Museum includes an impressive selection of Medieval Arts, pre and post 20th Century Polish Arts and works by foreign painters. the historical works by Jan Metejko are especially good.
The monument to Ghetto Heroes and the Path of Remembrance is very moving and worth walking round and if the weather is good the parks, such as Saxon Gardens, are lovely to walk around.
Do try some Polish flavoured vodka - strong and wonderful!