Most Swietokrzyski in front of Stadion Narodowy.
I have to say that I really enjoy Poland the most during the early morning and late evening. Also, the seasons affect it too. During the summer, it's hot and full of horrible tourists (I grew up in a tourist town and now see them as nothing more than walking wallets who complain.) Before the dawn, the only people out on the streets are the partiers going home (two men asked me—at 7:15 AM—where they could find a bar/club. I told them to go to Przekaski Zakaski.) and the really early-birds.
I was blessed with having a clear morning. There were wisps of clouds, but the sun shone through. It's really nice to see the morning dew on the ground and the morning fog settled between the buildings and the trees. Plac Zamkowy offers an excellent view of the sunrise. Once I find a better place, I'll let you all know.