Altenthann Castle, also known as Thann Castle, is a former hilltop castle at 432 m above sea level. NHN in Altenthann at today's Ochenbrucker Straße 4 at the site of today's church in the community of Schwarzenbruck in the Nürnberger Land district and is considered the headquarters of the Reich Ministerials of Altenthann.
Today's church tower, repeatedly interpreted as the keep of the old castle, has nothing in common with the Hohenstaufen complex and, according to the excavation results, was supposedly only built after the 15th century. The transition from castle to chapel use in the course of the 13th or 14th century cannot be dated in more detail. The archaeologically proven St. Nicholas Chapel had a modest footprint and does not follow on from the previous castle phase. Rather, the valuable humpback blocks must have been transported away because this was the only way to create space for the small chapel. Several years or decades may have passed between the end of the castle's use and the construction of the first chapel. A chronological sequence of Altenthann and Burgthann cannot be proven archaeologically; it is conceivable that the two castle complexes were temporarily next to each other
Source: Wikipedia