It's often interesting to look into different belief systems. A trip to St. Johns Church is a superb way to get to know one of the local religions.
You're spoiled for sightseeing choice when in Saalfeld-Saale. St. John's Church is a great place to kick off here, but there are plenty of other worthwhile sights to discover. Saalfeld Fairy Grottoes, Friedrich-Froebel Museum, and Greifenstein Castle are not far from the house of prayer and will fill in your day nicely.