One of our favorite things to do in Krakow is walk along the Planty, sometimes we even run the entire 4k or bike it with friends. It is technically considered a city park, one of the largest in Krakow, but what makes it unique is that it encircles the entire Old Town, Wawel Castle included. Walls protecting the city used to stand here, as can be seen when visiting the Barbican, but those walls were taken down in the 19th century by the city government and the moat was filled in to create the Planty.
Throughout the planty you can find benches to sit and relax, along with a lot of significant statues and artwork. There are also beautiful cafes to sit and have something to eat or drink (our favorite is Bunkier Cafe), and a few churches to visit, in addition to the main tourist attractions The Planty encircles.
If you want to take a bike ride around the Planty, you can rent bikes through the KMK city bike program. With stations all over the city, free for the first 20 minutes, and less than 1 Euro per hour they are perfect for a short tour around the Old Town.