The best view over Kraków is from the tethered balloon with viewing platform, located on the edge of the river Wisła/Vistula. The balloon ascends to a height of around 200 meters, and the panoramic view is unrivaled in the city.
View Gallery
View Gallery
From this vantage point you have a great view of Wawel Castle, over the roof tops of the Old Town to Nowa Huta in one direction and Wolski Forest in the other. Flights take place regularly, but they do depend on weather conditions, so it's best to check beforehand whether they are running or not.
Check their FB page for special deals. The balloon is located near Rondo Grunwaldzkie, just look up as its usually visible from anywhere in the city.