If you want to compare Petershagen in the Tolkiens' time (c. 1800) and today, see my comparision. And see how accurate was the older map! Tolkiens' street, Letztegasse is first one from the left. Today we can see there three houses from c. 19th century.
And below comparision of two maps from the 19th century with the Tolkiens' house at Letztegasse No. 28:
And below comparision of two maps from the 19th century with the Tolkiens' house at Letztegasse No. 28: