You may struggle to find an apartment in a better location than Eva and David's. On stepping out of the front door, steps to Charles Bridge were to the left and the beautiful Kampa park was to the right. The mostly pedestrian street had a lovely cheerful buzz during the day and was mostly quiet overnight. I had the windows open the entire time which gave me a nice breeze and the music of buskers during the day.
There are many spots on the riverfront within metres of the apartment that are perfect for relaxing and resting that remain free from the crazy tourist crowds.