Fantastic apartment on the edge of Petrin Park. It's a 20-25 min walk across Charles Bridge to Old Town Square so still very close to anything you may want to see/do in Prague.
Josef is very responsive to all messages, and provides a very detailed guidebook prior to your arrival in the city. It was great knowing where the locals like to eat/drink instead of winding up at a tourist bar.
I would recommend staying at this apartment, whether it's just for one night or a week.