If you're after a calm and quiet place to spend some time, make your way to St. Peter Catholic Church. This house of prayer offers a welcome break from the busy routine of life.
When you've spent a bit of time at this house of prayer in Halden, why not make your way to Fredriksten Fortress, Vanninga, and Rød Herregård? They're near St. Peter Catholic Church and also a hit with many tourists.