I think a visit to Krakow is not complete without a walk on Kanonicza street by night. Though located just off the Royal Way and the noisy Grodzka street, it offers not only refuge - but a sense of travelling back in time.
This street, paved with cobblestones gets very romantic after dark. Even though it's short, a twist hides you from your final destination - the royal castle (by the way, it's the entrance from Kanonicza that's most popular).
And, if you want to sit for a while - there are a few decent cafes and restaurant - including one of Krakow's pearls, the Copernicus (yes, Krakow University is where he graduated from).