Rae is correct. I lived in Warsaw for three years and loved almost every minute of it.

If you just got back, you probably had great weather. And everything was probably green and lovely.

For follow up trips. Krakow is the obvious next step. After that, probably the tri-cities of Gdansk, Gdynia, and Sopot. For a longer trip to Poland, these (Krakow to the South of Warsaw, and the tri-cities to the North) are all accessible from Warsaw via the high-speed 'Pendolino' train. Going North to South from Warsaw is easy - east to west typically requires longer train trips or longer drives.